Bioaccessibility of Microplastic-Associated Antibiotics in Freshwater Organisms: Highlighting the Impacts of Biofilm Colonization via an In Vitro Protocol.

Microplastics in the environment can be colonized by microbes capable of forming biofilms, which may act as reactive coatings to affect the bioaccessibility of pollutants in organisms. This study investigated the dynamic evolution of biofilm colonization on microplastics and its impacts and mechanisms on the bioaccessibility of microplastic-associated sulfamethazine (SMT) via microcosm incubation in surface water and sediment. After 60 days of incubation, the microbial communities formed in microplastics were distinct and more diverse than those untethered in surroundings, and photoaging treatment decreased the affinity of biofilms on microplastics due to decreased hydrophobicity. Biofilm formation further enhanced the desorption and bioaccessibility of microplastic-sorbed SMT in organisms. In vitro experiments indicated that the critical effects were mainly related to the stronger interaction of gastrointestinal components (i.e., pepsin, bovine serum albumin (BSA), and NaT) with biofilm components (e.g., extracellular polymer substances) than with the pure surface of microplastics, which competed for binding sites in microplastics for SMT more significantly. Photoaging decreased the enhancing effects of biofilms due to their lower accumulation in aged microplastics. This study is the first attempt to reveal the role of biofilms in the bioaccessibility of microplastics with associated antibiotics and provide insights into the combined risk of microplastics in the environment.

Effect of sulfamethazine on anaerobic digestion of manure mediated by biochar.

Antibiotic contamination from animal production and wastewater treatment process will release antibiotic resistant genes to the environment and potentially threaten human health. Meanwhile, the residual antibiotic in manure could have inactive impacts on anaerobic digestion (AD). This study explores the effect of sulfamethazine on manure AD mediated by biochar. The results show that biochar weakens the adverse effects of sulfamethazine on AD by adsorption sulfamethazine during the initial stage (0-3 days) of AD and promoting the growth of hydrolytic bacteria (especially Firmicutes and Bacteroidetes) and methanogens (especially Methanothrix and Methanosarcina). Besides, the presence of biochar improves the biogas production capacity of AD and promotes microbial diversity and community richness. Thus, the addition of biochar greatly reduces sulfamethazine and is testified to be a desirable strategy to mitigate the inhibition of sulfamethazine on AD.

Evaluating the net effect of sulfadimidine on nitrogen removal in an aquatic microcosm environment.

Antibiotics enter into aquatic pond sediments by wastewater and could make detrimental effects on microbial communities. In this study, we examined the effects of sulfadimidine on nitrogen removal when added to experimental pond sediments. We found that sulfadimidine increased the number of sulfadimidine resistant bacteria and significantly increased the abundance of sul2 at the end of the incubation time (ANOVA test at Tukey HSD, P < 0.05). In addition, sulfadimidine decreased the N2O reduction rate as well as the amount of nitrate reduction. Pearson correlation analysis revealed that the N2O reduction rate was significantly and negatively correlated with narG (r = -0.679, P < 0.05). In contrast, we found a significant positive correlation between the amount of nitrate reduction and the abundance of narG (r = 0.609, P < 0.05) and nirK (r = 0.611, P < 0.05). High-throughput sequencing demonstrated that Actinobacteria, Euryarchaeota, Gemmatimonadetes, Nitrospirae, Burkholderiaceae (a family of Proteobacteria), and Thermoanaerobaculaceae (a family of Firmicutes) decreased with sulfadimidine exposure. In sediments, Actinobacteria, Bacteroidetes, Cyanobacteria, Epsilonbacteraeota, Euryarchaeota, Firmicutes, Gemmatimonadetes, and Spirochaetesat may play key roles in nitrogen transformation. Overall, the study exhibited a net effect of antibiotic exposure regarding nitrogen removal in an aquatic microcosm environment through a combination of biochemical pathways and molecular pathways, and draws attention to controlling antibiotic pollution in aquatic ecosystems.

Separate and joint eco-toxicological effects of sulfadimidine and copper on soil microbial biomasses and ammoxidation microorganisms abundances.

Heavy metals and antibiotics residues in agricultural soils are attracting more and more attention. A laboratory study was conducted to evaluate the single and combined effects of sulfadimidine (SM2) (0.05, 0.20, 0.80 mmol/kg) and copper (Cu) (1.60 mmol/kg) on soil microbial biomasses and ammoxidation microorganisms abundances after 7, 14, 21 and 28 days. The results demonstrated that the single and combined contaminations had a significant and persistent inhibitory effect on soil bacteria, fungi and actinomycetes populations and amoA gene copies of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) (Except SM2 0.05 and 0.20 mmol/kg on 7 and 14 d and SM2 0.05 mmol/kg on 21 d led to a stimulatory effect on fungi and AOA-amoA gene, respectively). With higher dosage and longer exposure time, the toxic effect of single and combined contaminants on soil bacteria, fungi and actinomycetes as well as on the amoA gene of AOA and AOB was greatly reinforced. Combined contaminants produced more toxicity than the chemicals were used alone. Overall, the interaction effects of SM2 and Cu on bacteria (on 14, 21 and 28 d), fungi and AOA-amoA were mainly synergism, in contrast, on actinomycetes (on 14, 21 and 28 d) and AOB-amoA were mainly antagonism. The order of the toxic effects of the single Cu and combined contaminants on microbial activity was: bacteria > actinomycetes > fungi. Furthermore, AOB-amoA was more sensitive to both contaminants toxicity than AOA-amoA, while AOA-amoA gene copies were greater than AOB-amoA gene copies about one order of magnitude.

Effects of tylosin, ciprofloxacin, and sulfadimidine on mcrA gene abundance and the methanogen community during anaerobic digestion of cattle manure.

This study evaluated how tylosin (TYL), ciprofloxacin (CIP), and sulfadimidine (SM2) affected biogas and CH4 production during anaerobic digestion (AD) via their effects on the key genes related to methane production and the methanogenic community. The results showed that TYL, CIP, and SM2 reduced the production of methane during AD by 7.5%, 21.9%, and 16.0%, respectively. After AD for five days, CIP strongly inhibited the mcrA gene, where its abundance was 49% less than that in the control. TYL and SM2 decreased the abundances of Spirochaeta and Fibrobacteres during AD. High-throughput sequencing identified 10 methanogen genera, where Methanocorpusculum, Methanobrevibacter, and Methanosarcina accounted for 99.1% of the total archaeal reads. TYL and SM2 increased the efficiency of the acetoclastic methanogen pathway (Methanosarcina) by 29.04% and 52.79%, respectively. Redundancy analysis showed that Spirochaeta, Fibrobacteres, and Methanosarcina had positive correlations with CH4 and mcrA. We found that 30 mg kg-1 CIP had a strong inhibitory effect on methane production by influencing the abundances of Methanobrevibacter and Methanosarcina during AD.

Correlation between antibiotic-induced feeding depression and body size reduction in zooplankton (rotifer, Brachionus calyciflorus): Neural response and digestive enzyme inhibition.

The study analyzed the correlation between the antibiotic-induced feeding depression and body size reduction in rotifer, Brachionus calyciflorus, involving exposure, post-exposure and re-exposure periods. The filtration and ingestion rates of the rotifers were inhibited in these three exposure periods at any given concentration of the antibiotic sulfamethazine (SMZ). As food for rotifer, the cell size of the green algae was unchanged, which indicated that it could not drive feeding depression. Secondly, several corresponding physiological responses were considered. Reactive oxygen species (ROS) levels increased in the post-exposure and the re-exposure; acetylcholinesterase (AChE) activity was significantly decreased in the exposure and the re-exposure, whereas it was induced in the post-exposure. The activities of amylase and lipase were always inhibited in these three exposure periods. Additionally, significant decreases in lorica length, width and biovolume of rotifers occurred after the feeding depression. Statistical analysis indicated a positive correlation between the activity of the digestive enzyme and the body size. Our results demonstrated that SMZ could influence the neurotransmission, inhibit the activity of the digestive enzyme, and finally result in body size reduction. These results provided an integrated perspective on assessing the toxicity effects of antibiotic in non-lethal dosage on the feeding behavior of non-target aquatic organisms.

Copper complex with sulfamethazine and 2,2'-bipyridine supported on mesoporous silica microspheres improves its antitumor action toward human osteosarcoma cells: cyto- and genotoxic effects.

Ideal drugs to cure cancer leave normal cells unharmed while selectively turning tumor cells unviable. Several copper complexes have been able to selectively slow down tumor proliferation. We hypothesized that Cu(smz)2(bipy)·H2O (1)-a copper-complex that has two ligands capable of interacting with DNA-would outperform Cu(smz)2(OH2)·2H2O (2), and also that supporting 1 on mesoporous silica spheres would decrease even further tumor cell viability in vitro. After exposing osteosarcoma cells (MG-63) and normal phenotype cells of bone origin (MC3T3-E1) to either complex, we studied their toxic effect and mechanisms of action. We determined cell viability (MTT assay) and quantified formation of reactive oxygen species (oxidation of DHR-123 to rhodamine). Moreover, we assessed genotoxicity from (i) formation of micronucleus (MN assay) and (ii) damage of DNA (Comet assay). After the exposure of 1 supported on silica spheres, we tested cell viability. Our results confirm our hypotheses: inhibition of tumor cells follows: supported 1 > dissolved 1 > 2. Future work that enhances the load of the complex exclusively in mesopores may improve the ability of 1 to further inhibit tumor cell viability.

Sulphamethazine derivatives as immunomodulating agents: New therapeutic strategies for inflammatory diseases.

Sulfamethazine (SMZ) (1) is an antibacterial sulfa drug which suppresses the synthesis of dihydrofolic acid. It is used for the treatment of infections in livestock; such as gastrointestinal, and respiratory tract infections. During the current study, synthesis, characterization, and evaluation of immunomodulatory activities of derivatives of sulfamethazine (SMZ) (3-39) was carried out. These derivatives were synthesized by the reaction of sulfamethazine with a range of acid chlorides. All the compounds were characterized by using modern spectroscopic techniques, such as 1H-, and 13C-NMR, EI-MS, and HRFAB-MS. Compounds 3-10, 14, and 15 were identified as new compounds. Immunomodulatory effect of compounds 3-39 on different parameters of innate immune response was evaluated, including the production of Reactive Oxygen Species (ROS) from human whole blood and isolated polymorphonuclear neutrophils (PMNs), nitric oxide (NO), and pro-inflammatory cytokine TNF-α. All the new compounds, except 14 and 15, showed a significant anti-inflammatory activity. Compounds 3-39 were also evaluated for their anti-bacterial activity and cytotoxicity (3T3 mouse fibroblast cell lines). All the compounds were found to be non-cytotoxic against normal cell lines.

Effect of different sulfadimidine addition methods on its degradation behaviour in swine manure.

Sulfadimidine (SM2) is commonly used in the swine industry and enters the environment via faeces. In recent years, advances in the ecotoxicology of SM2 have become a popular research interest with two common research methods including swine manure collection from swine fed with a diet containing SM2 and directly adding SM2. The purpose of this experiment was to compare SM2 degradation behaviour in pig manure with two different SM2 addition methods. The results showed that the degradation half-lives of SM2 in manure from SM2-fed swine treatment were 33.2 and 32.0 days at the initial addition level of SM2 at 32.1 and 64.3 mg/kg, respectively. This was significantly longer than that in manure directly adding SM2 treatment with the half-lives of 21.4 and 14.8 days. The metabolite of SM2 N4-acetyl-sulfamethazine occurred in manure from SM2-fed swine treatment but was not detected in directly adding SM2 treatment. The pH in manure from SM2-fed swine treatment was significantly lower than that in directly adding SM2 treatment, but the values of organic carbon, total nitrogen, and electrical conductivity in manure from SM2-fed swine treatment were significantly higher than those in manure directly adding SM2 treatment. Meanwhile, although the copy number of bacteria had no significant difference between two treatments, there was a significant difference in bacteria diversity. Results of the present study demonstrated that the presence of the metabolites, chemical property, and microbial diversity might be the reason for different SM2 degradation behaviours on different addition methods. Thus, the method using manure with SM2 collected from swine could obtain more accurate results for the ecotoxicological study of SM2.

Sulfamethazine-based pH-sensitive hydrogels with potential application for transcatheter arterial chemoembolization therapy.

UNLABELLED: Transcatheter arterial chemoembolization (TACE) is the most common palliative therapy for unresectable hepatocellular carcinoma (HCC). The conventional TACE technique, which employs the Lipiodol® emulsion, has been widely used for human cancer treatments. However, this delivery system seems to be inconsistent and unstable in maintaining a high concentration of drugs at tumor sites. An alternative approach for TACE is loading drugs into a liquid embolic solution that exists as an injectable solution and can exhibit a sol-to-gel phase transition to form a solidified state once delivered to the tumor site. Here, we develop a novel sulfamethazine-based anionic pH-sensitive block copolymer with potential application as a radiopaque embolic material. The copolymer, named PCL-PEG-SM, and comprised of poly(ε-caprolactone), sulfamethazine, and poly(ethylene glycol), was fabricated by free radical polymerization. An aqueous solution of the developed copolymer underwent a sol-to-gel phase transition upon lowering the environmental pH to create a gel region that covered the physiological condition (pH 7.4, 37°C) and the low pH conditions at tumor sites (pH 6.5-7.0, 37°C). The release of doxorubicin (DOX) from DOX-loaded copolymer hydrogels could be sustained for more than 4weeks in vitro, and the released DOX retained its fully bioactivity via inhibition the proliferation of hepatic cancer cells. The radiopaque embolic formulations that were prepared by mixing copolymer solutions at pH 8.0 with Lipiodol®, a long-lasting X-ray contrast agent, could exhibit the gelation inside the tumor after intratumoral injection or intraarterial administration using a VX2 carcinoma hepatic tumor rabbit model. These results suggest that a novel anionic pH-sensitive copolymer has been developed with a potential application as a liquid radiopaque embolic solution for TACE of HCC. STATE OF SIGNIFICANCE: Transcatheter arterial chemoembolization (TACE) has been widely used as a palliative treatment therapy for unresectable hepatocellular carcinoma (HCC). Conventional TACE technique, which usually employs emulsion of DOX-in-Lipiodol®, followed by an embolic agent, has significant limitation of inconsistency and lack of controlled release ability. To address these limitations of conventional TACE material system, we introduced a novel liquid radiopaque embolic material from our pH-sensitive hydrogel. The material has low viscosity that can be injected via a microcatheter, rather biocompatibility, and drug controlled release ability. Importantly, it can form gel in the tumor as well as tumoral vasculature in response to the lowered pH at the tumor site, which proved the potential for the use to treat HCC by TACE therapy.

Modelling and shadowgraph imaging of cocrystal dissolution and assessment of in vitro antimicrobial activity for sulfadimidine/4-aminosalicylic acid cocrystals.

PURPOSE: The aim of this work was to evaluate the influence of crystal habit on the dissolution and in vitro antibacterial and anitiprotozoal activity of sulfadimidine:4-aminosalicylic acid cocrystals. METHODS: Cocrystals were produced via milling or solvent mediated processes. In vitro dissolution was carried out in the flow-through apparatus, with shadowgraph imaging and mechanistic mathematical models used to observe and simulate particle dissolution. In vitro activity was tested using agar diffusion assays. RESULTS: Cocrystallisation via milling produced small polyhedral crystals with antimicrobial activity significantly higher than sulfadimidine alone, consistent with a fast dissolution rate which was matched only by cocrystals which were milled following solvent evaporation. Cocrystallisation by solvent evaporation (ethanol, acetone) or spray drying produced flattened, plate-like or quasi-spherical cocrystals, respectively, with more hydrophobic surfaces and greater tendency to form aggregates in aqueous media, limiting both the dissolution rate and in vitro activity. Deviation from predicted dissolution profiles was attributable to aggregation behaviour, supported by observations from shadowgraph imaging. CONCLUSIONS: Aggregation behaviour during dissolution of cocrystals with different habits affected the dissolution rate, consistent with in vitro activity. Combining mechanistic models with shadowgraph imaging is a valuable approach for dissolution process analysis.

Contamination of sulfonamide antibiotics and sulfamethazine-resistant bacteria in the downstream and estuarine areas of Jiulong River in Southeast China.

Surface water samples from downstream and estuarine areas of Jiulong River were collected in August 2011 and May 2012 for detecting sulfonamide antibiotic residues and isolating sulfamethazine-resistant bacteria. Sulfamethazine was detected in all samples in May 2012 at an average concentration of 78.3 ng L(-1), which was the highest among the nine sulfonamide antibiotics determined. Sulfamethazine-resistant bacteria (SRB) were screened using antibiotic-containing agar plates. The SRB average abundance in the samples was 3.69 × 10(4) and 2.17 × 10(3) CFUs mL(-1) in August 2011 and May 2012, respectively, and was positively correlated to sulfamethazine concentration in May 2012. The 16S rRNA gene sequencing of all the 121 SRB isolates revealed high diversity. Furthermore, the SRB isolates exhibited multidrug resistance, with 48.7% showing resistance to at least three antibiotics. The abundance and persistence of highly diverse SRB and their multidrug resistance are likely to demonstrate the transferable pressure from coastal environments on public health.

Effects of sulfamethazine on denitrification and the associated N2O release in estuarine and coastal sediments.

Denitrification is an important pathway of nitrogen removal and nitrous oxide (N2O) production in estuarine and coastal ecosystems, and plays a significant role in counteracting aquatic eutrophication induced by excessive nitrogen loads. Estuarine and coastal environments also suffer from increasing antibiotic contamination because of the growing production and usage of antibiotics. In this study, sediment slurry incubation experiments were conducted to determine the influence of sulfamethazine (SMT, a sulphonamide antibiotic) on denitrification and the associated N2O production. Genes important for denitrification and antibiotic resistance were quantified to investigate the microbial physiological mechanisms underlying SMT's effects on denitrification. SMT was observed to significantly inhibit denitrification rates, but increasing concentrations of SMT enhanced N2O release rates. The negative exponential relationships between denitrifying gene abundances and SMT concentrations showed that SMT reduced denitrification rates by restricting the growth of denitrifying bacteria, although the presence of the antibiotic resistance gene was detected during the incubation period. These results imply that the wide occurrence of residual antibiotics in estuarine and coastal ecosystems may influence eutrophication control, greenhouse effects, and atmospheric ozone depletion by inhibiting denitrification and stimulating the release of N2O.

Deep-brain photoreceptors (DBPs) involved in the photoperiodic gonadal response in an avian species, Gallus gallus.

Three primitive photoreceptors [melanopsin (Opn4), neuropsin/opsin5 (Opn5) and vertebrate ancient opsin (VAOpn)] were reported as possible avian deep-brain photoreceptors (DBPs) involved in the perception of photoperiodic information affecting the onset and development of reproduction. The objective of this study was to determine the effect of long-day photostimulation and/or sulfamethazine treatment (SMZ, a compound known to advance light-induced testes development) on gene expression of DBPs and key hypothalamic and pituitary genes involved in avian reproductive function. Two-week old chicks were randomly selected into four experimental groups: short-day control (SC, LD8:16), short-day+SMZ (SS, LD8:16, 0.2% diet SMZ), long-day control (LC, LD16:8), and long-day+SMZ (LS, LD16:8, 0.2% diet SMZ). Birds were sampled on days 3, 7, and 28 after initiation of a long-day photoperiod and/or SMZ dietary treatments. Three brain regions [septal-preoptic, anterior hypothalamic (SepPre/Ant-Hypo) region, mid-hypothalamic (Mid-Hypo) region, posterior-hypothalamic (Post-Hypo) region], and anterior pituitary gland were dissected. Using quantitative real-time RT-PCR, we determined changes of expression levels of genes in distinct brain regions; Opn4 and Opn5 in SepPre/Ant-Hypo and Post-Hypo regions and, VAOpn in the Mid-Hypo region. Long-day treatment resulted in a significantly elevated testes weight on days 7 and 28 compared to controls, and SMZ augmented testes weight in both short- and long-day treatment after day 7 (P<0.05). Long-day photoperiodic treatment on the third day unexpectedly induced a large 8.4-fold increase of VAOpn expression in the Mid-Hypo region, a 15.4-fold increase of Opn4 and a 97.8-fold increase of Opn5 gene expression in the Post-Hypo region compared to SC birds (P<0.01). In contrast, on days 7 and 28, gene expression of the three DBPs was barely detectable. LC group showed a significant increase in GnRH-1 and TRH mRNA in the Mid-Hypo compared to SC on day 3. Pituitary LHß and FSHß mRNA were significantly elevated in LC and LS groups compared to SC on days 3 and 7 (P<0.05). On days 3 and 7, TSHß mRNA level was significantly elevated by long-day treatment compared to the SC groups (P<0.05). Results suggest that long-day photoperiodic activation of DBPs is robust, transient, and temporally related with neuroendocrine genes involved in reproductive function. Additionally, results indicate that two subsets of GnRH-1 neurons exist based upon significantly different gene expression from long-day photostimulation and long-day plus SMZ administration. Taken together, the data indicate that within 3 days of a long-day photoperiod, an eminent activation of all three types of DBPs might be involved in priming the neuroendocrine system to activate reproductive function in birds.

Sulfa drugs as inhibitors of carbonic anhydrase: new targets for the old drugs.

Sulfa drugs are well-known antibacterial agents containing N-substituted sulfonamide group on para position of aniline ring (NH2RSO2NHR'). In this study 2,4-dichloro-1,3,5-triazine derivatives of sulfa drugs, sulfamerazine (1b), sulfaquinoxaline (2b), sulfadiazine (3b), sulfadimidine (4b), and sulfachloropyrazine (5b) (1a-5a) were synthesized and characterized. Their carbonic anhydrase inhibition activity was evaluated against bovine cytosolic carbonic anhydrase isozyme II (bCA II). For the sake of comparison the CA inhibition activity of the parent sulfa drugs (1b-5b) was also evaluated. A significant increase in CA inhibition activity of sulfa drugs was observed upon substitution with 2,4-dichloro-1,3,5-triazine moiety. Molecular docking studies were carried out to highlight binding site interactions. ADME properties were calculated to evaluate drug likeness of the compounds.

Selective coordination ability of sulfamethazine Schiff-base ligand towards copper(II): molecular structures, spectral and SAR study.

In the present work, a combined experimental and theoretical study of the N-(4,6-Dimethyl-pyrimidin-2-yl)-4-[(2-hydroxy-benzylidene)amino]benzenesulfonamide ligand (H2L) and its mononuclear and magnetically diluted binuclear Cu(II) complexes has been performed using IR, TG/DTA, magnetic, EPR, and conductivity measurements. Calculated g-tensor values showed best agreement with experimental values from EPR when carried out using the MPW1PW91 functional. Coordination of H2L to a Cu(II) center, regardless of the binding site and Cu:L stoichiometry, leads to a significant decrease in the antibacterial activity compared to the free ligand as well as reference drugs in the case of Staphylococcus aureus. Structural-activity relationship suggests that ELUMO, ΔE, dipole moment, polarizability and electrophilicity index were the most significant descriptors for the correlation with the antibacterial activity.

The effects of the antibiotics ampicillin, florfenicol, sulfamethazine, and tylosin on biogas production and their degradation efficiency during anaerobic digestion.

The impacts of four common animal husbandry antibiotics (ampicillin, florfenicol, sulfamethazine, and tylosin) on anaerobic digestion (AD) treatment efficiency and the potential for antibiotic degradation during digestion were evaluated. Sulfamethazine and ampicillin exhibited no impact on total biogas production up to 280 and 350 mg/L, respectively, although ampicillin inhibited biogas production rates during early stages of AD. Tylosin reduced biogas production by 10-38% between 130 and 913 mg/L. Florfenicol reduced biogas by ≈ 5%, 40% and 75% at 6.4, 36 and 210 mg/L, respectively. These antibiotic concentrations are higher than commonly seen for mixed feedlot manure, so impacts on full scale AD should be minimal. Antibiotic degradation products were found, confirming AD effectively degraded ampicillin, florfenicol, and tylosin, although some products were persistent throughout the process. Contamination of AD solid and liquid effluents with sulfamethazine and antibiotic transformation products from florfenicol and tylosin could present an environmental concern.

Molecular cloning and expression analysis of cytochrome P450 3A gene in the turbot Scophthalmus maximus.

In this study, the cytochrome P450 3A (CYP3A) gene was cloned from the turbot Scophthalmus maximus for the first time using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends approaches. The amino acid sequences were analyzed with corresponding software programs. The cDNA of CYP3A was 1,969 bp in length, which contained a 5'-untranslated region (UTR) of 34 bp, a 3'-UTR of 404 bp and an open reading frame of 1,530 bp encoding a predicted protein of 509 amino acids (GenBank accession No. JN216889). The deduced protein had a molecular weight of 58.09 kDa and an isoelectric point of 5.75. Amino acid sequence alignment indicated that turbot CYP3A shared 60-67% homology with other fish species. It consists of a signal peptide, six conservative substrate recognition sites (SRS 1-6) and the conserved heme-binding motif FXXGXXXCXG in all CYP3As. Quantitative real-time RT-PCR analysis indicated that turbot CYP3A mRNA was widely expressed in liver, kidney, gill, muscle, stomach, intestine, gallbladder and spleen, with the highest level in liver and the lowest in muscle. After oral administration of sulfamethazine, CYP3A expression in all experimental groups enhanced compared with control, and the expression varied with administration time. It suggested that CYP3A expression could be induced by sulfamethazine. Our findings provided molecular characterization and expression profile of turbot CYP3A, and revealed the important role that turbot CYP3A played in drug metabolisms.

Sulfamethazine suppresses epigenetic silencing in Arabidopsis by impairing folate synthesis.

DNA methylation is a critical, dynamically regulated epigenetic mark. Small chemicals can be valuable tools in probing cellular processes, but the set of chemicals with broad effects on epigenetic regulation is very limited. Using the Arabidopsis thaliana repressor of silencing1 mutant, in which transgenes are transcriptionally silenced, we performed chemical genetic screens and found sulfamethazine (SMZ) as a chemical suppressor of epigenetic silencing. SMZ treatment released the silencing of transgenes as well as endogenous transposons and other repetitive elements. Plants treated with SMZ exhibit substantially reduced levels of DNA methylation and histone H3 Lys-9 dimethylation, but heterochromatic siRNA levels were not affected. SMZ is a structural analog and competitive antagonist to p-aminobenzoic acid (PABA), which is a precursor of folates. SMZ decreased the plant folate pool size and caused methyl deficiency, as demonstrated by reductions in S-adenosylmethionine levels and in global DNA methylation. Exogenous application of PABA or compounds downstream in the folate biosynthesis pathway restored transcriptional silencing in SMZ-treated plants. Together, our results revealed a novel type of chemical suppressor of epigenetic silencing, which may serve as a valuable tool for studying the roles and mechanisms of epigenetic regulation and underscores an important linkage between primary metabolism and epigenetic gene regulation.

Bovine respiratory disease: efficacy of different prophylactic treatments in veal calves and antimicrobial resistance of isolated Pasteurellaceae.

The present study was conducted to evaluate the efficacy of two prophylactic antibiotic treatments against bovine respiratory disease (BRD) in veal calves. In addition, the antibiotic susceptibilities of isolated Pasteurellaceae were tested. The calves were treated either on the day of arrival by a single administration of tulathromycin (group A, n=20), by a peroral administration of chlortetracycline, sulphadimidine, and tylosin (group B, n=20) for seven consecutive days, or were not prophylactically treated (group C, n=19). On the first day of clinically diagnosed BRD, transtracheal lavage samples were obtained prior to therapeutic treatment and were subsequently cultured. Pasteurellaceae isolates were tested for their susceptibility to 12 antimicrobial agents by the determination of the minimal inhibitory concentrations. During the first 56 d after arrival, different calves in group A and B suffered from one episode of clinically diagnosed BRD while calves of group C experienced two episodes. The average daily weight gain during the same period was significantly lower in group C (0.89 ± 0.04kg/d) than in the two prophylactically treated groups (1.14 ± 0.05 and 1.15 ± 0.04 kg/d for group A and B, respectively). The improved performance of groups A and B in comparison to group C could be related to a lower incidence of respiratory disorders during the first days after arrival in the prophylactically treated animals. No differences in the clinical efficacy were seen between the two tested prophylactic treatments. The most prevalent bacterial pathogens isolated (n=79) were Pasteurella multocida (23% of isolated pathogens), Mycoplasma bovis (18%), and Mannheimia varigena (16%). For the isolated Pasteurellaceae, a high resistance pattern was observed to tylosin (83% of the tested P. multocida and 88% of the Mannheimia spp. isolates resistant) and tilmicosin (56% of the tested P. multocida isolates non-sensitive).