Effective one-component model of binary mixture : molecular arrest induced by the spatially correlated stochastic dynamics

Spatially correlated noise (SCN), i.e. the thermal noise that affects neighbouring particles in a similar manner, is ubiquitous in soft matter systems. In this work, we apply the over-damped SCN-driven Langevin equations as an effective, one-component model of the dynamics in dense binary mixtures. We derive the thermodynamically consistent fluctuation-dissipation relation for SCN to show that it predicts the molecular arrest resembling the glass transition, i.e. the critical slow-down of dynamics in the disordered phases. We show that the mechanism of singular dissipation is embedded in the dissipation matrix, accompanying SCN. We are also able to identify the characteristic length of collective dissipation, which diverges at critical packing. This novel physical quantity conveniently describes the difference between the ergodic and non-ergodic dynamics. The model is fully analytically solvable, one-dimensional and admits arbitrary interactions between the particles. It qualitatively reproduces several different modes of arrested disorder encountered in binary mixtures, including e.g. the re-entrant arrest. The model can be effectively compared to the mode coupling theory

Polymer shape dynamics induced by spatially correlated noise

In this paper, we examine the influence of a spatially correlated noise on a 2D polymer-like particle. The molecule is modeled with harmonic potential for bonds and angular interactions and a global Lennard–Jones potential. We present a method for generating a spatially correlated noise if the time and spatial terms in the correlation function factorize. The dynamics of polymer’s shape transformation process is investigated by means of Fourier analysis. An increase in correlation length results in the environmentally induced stiffening of the chain

Reinterpreting polymer unfolding effect induced by a spatially correlated noise

This paper provides additional insight into the effect of spontaneous unfolding of the model polymeric chain driven by spatially correlated noise, described in M. Majka, P.F. Góra, Phys. Rev. E86, 051122 (2012). We examine the statistical data on the linearized chain substructures to find that the global unfolding effect arises mainly from the cumulation of short, 2-segment-long fragments, scattered along the chain. This supports an alternative view of spatially correlated noise as both the source of disturbance and the conformation preserving factor

Cyclopenta[c]phenanthrene induction of CYP1A in brain of rainbow trout (Oncorhynchus mykiss)

We assessed the effects of cyclopenta[c]phenanthrene (CP[c]Ph) and benzo[a]pyrene (B[a]P; positive control) on CYP1A gene expression in brain of juvenile rainbow trout (Oncorhynchus mykiss) using the quantitative reverse transcription polymerase chain reaction (Q-RT-PCR). A group of hatchery raised rainbow trout, with an average body mass of 49.4 g and total length of 15.5 cm were given an intraperitoneal injection (10 mg*kg-1) of either CP[c]Ph or B[a]P in corn oil (2 mg*mi-1 corn oil) or corn oil alone (control). After 24 and 48 h, trout brains were collected for mRNA isolation and analysis. After 24 hours of the exposure, only B[a]P-treated rainbow trout had 10-fold higher number of CYP1A transcripts (mean = 3.63*106 transcripts*µg-1 total RNA) than control fish (3.24*105 transcripts*µg-1 total RNA; Tukey test, P<0.05). After 48 hrs, significantly higher levels of CYP1A expression (Tukey test, P<0.001) were found in either CP[c]Ph- or B[a]P- induced group (1.45*106 and 6.92*106 transcriptsźµg-1 total RNA, respectively) over a control group (mean=1.41*105 transcripts*µg-1 total RNA). The finding that CYP1A in brain tissue was inducible by CP[c]Ph, a polycyclic aromatic hydrocarbon (PAH) of different than B[a]P planar characteristics, may further validate the use of rainbow trout brain CYP1A mRNA levels as a biomarker of PAH exposure

Relative quantification of CYP1A gene expression in whitefish (Coregonus lavaretus) exposed to benzo[a]pyrene

The expression of CYP1A (cytochrome P4501A) can be induced by a number of aromatic compounds in teleost fishes. We developed a real-time PCR assay for measuring relative quantities (RQ) of CYP1A mRNA in whitefish (Coregonus lavaretus). To test for the usefulness of the assay we performed a treatment study, using benzo[a]pyrene (B[a]P) a model CYP1A inducer. Primers for the CYP1A gene were adapted from the literature, whereas those for [beta]-actin (endogenous control) were designed from a region that was found to be conserved among salmonid [beta]-actin genes. A group of hatchery raised whitefish, with an average body mass of 15 g and total length of 12 cm were given an intraperitoneal injection (10 mg/kg) of B[a]P in corn oil (2 mg B[a]P/ml corn oil) or corn oil alone (Control). After 48 h, whitefish liver, head kidney and brains were collected for mRNA isolation and analysis. In all three tissues sampled, CYP1A mRNA was affected by treatment with B[a]P. Head kidney tissue showed the greatest induction potential (RQ=11.00) from base levels (RQ=1.00), followed by liver (RQ=9.45), and brain (RQ=3.76). These results demonstrated that CYP1A was highly inducible by B[a]P in whitefish head kidney and liver, and to some extent, in brain tissue. The approach presented here has the advantage of providing rapid and accurate measures of CYP1A induction in various tissues of fish responding to PAH contaminant exposure

Oxidative metabolism, mutagenic and carcinogenic properties of some polycyclic aromatic hydrocarbons

This attempt to synthesize the present state of knowledge on the correlation between the structure of chosen PAHs and their mutagenic or carcinogenic activity shows that the dependencies cannot be treated univocally. Extreme complexity of the subject, typical for investigations on the boundary between chemistry and biology, inclines one to search for new ways of synthesis of new compounds, which would be of interest for biologists studying the problem of chemical carcinogenesis. On the other hand, there is a strong need for elaborating a standardized test that would explicitly define the carcinogenic properties of a specific compound. The use of a variety of methods for the determination of carcinogenic potency of chemical compounds combined with simultaneous differentiation of structure of examined compounds, sometimes leads to contradictory conclusions. Correlation between mutagenic and carcinogenic activity of some compounds is also sometimes questionable. Modern molecular biology should allow for elaborating a method which would give a satisfactory and reliable answer to the fundamental question: is a specific compound carcinogenous for a human organism? And if so - to what extent

Preliminary study on adverse effects of phenanthrene and its methyl and phenyl derivatives in larval zebrafish, Danio rerio

Toxic effects of polycyclic aromatic hydrocarbons (PAHs) have been extensively studied in fish, although knowledge concerning biological activities of phenanthrene and its derivatives remains still incomplete. The aim of this work was to evaluate lethal and sublethal effects of benzo(a)pyrene, phenanthrene and phenanthrene derivatives (1-methylphenanthrene, 4-methylphenanthrene, 1-phenylphenanthrene and 4-phenylphenanthrene) on zebrafish (Danio rerio) larvae. We conducted acute toxicity test, using 96h static renewal exposure to a series of the PAH concentrations (0.05, 0.50, 5.00, 50.00µmol*l-1), to determine the No Effect Concentration (NEC) value for each compound examined. The mean NEC estimates obtained in the study were 5.16۪.45µmol*l-1 (B[a]P), 4.88۪.13µmol*l-1 (Ph), 40.24䔰.93µmol*l-1 (1P-Ph), 47.92ۭ.61µmol*l-1 (1M-Ph), 24.31۱.33µmol*l-1 (4P-Ph) and 3.11۫.01µmol*l-1 (4M-Ph) and suggested the following order of PAH toxicities on Danio rerio larvae: 4M-Ph>Ph˜B[a]P>4PPhP-Ph>1M-Ph. To gain insight into possible molecular mechanisms of apparent toxicity of phenanthrene derivatives on zebrafish larvae, we examined mRNA expression of cyp1a, cyp1b1, and vtg genes in the larvae exposed for 48h to a PAH concentration of 0.50µmol*l-1. Whereas the larvae exposed to each tested PAH displayed many developmental abnormalities (i.e. pericardial and yolk sac edema, dorsal curvature, or tail malformations), no significant upregulation of cyp1a and cyp1b1 mRNA was observed, except for zebrafish exposed to B[a]P. However, significant reduction of vtg mRNA was observed in the larvae exposed to phenanthrene and its 4P- derivative. The results may contribute to the development of a new knowledge about effects of structurally diverse phenanthrene derivatives on vertebrate organisms

MicroRNA expression profiles in liver and colon of sexually immature gilts after exposure to Fusarium mycotoxins

To improve our knowledge of the role of microRNAs (miRs) in responses of the porcine digestive system to two Fusarium mycotoxins, zearalenone (ZEN) and deoxynivalenol (DON), we examined the expression of 7 miRs (miR-9, miR-15a, miR-21, miR-34a, miR-122, miR-125b, and miR-192), previously found to be deregulated in diseased liver and colon cells. In this study, immature gilts were exposed to NOEL doses of ZEN (40 μg/kg/d), DON (12 μg/kg/d), ZEN+DON (40+12 μg/kg/d), and placebo (negative control group) for 7, 14, 21, 28, 35, and 42 days. Before the treatment, expression levels of the selected miRs were measured in the liver, the duodenum, the jejunum, and the ascending and the descending colon of the gilts. Hierarchical clustering of the tissues by their miR expression profiles was consistent with what would be expected based on the anatomical locations and the physiological functions of the organs, suggesting that functions of the miRs are related to the specificities of the tissues in which they are expressed. A subset of 2 pairs of miRs (miR-21+miR-192 and miR-15a+miR-34a), which were assigned to two distinct clusters based on their tissue abundance, was then evaluated in the liver and the ascending and the descending colon during the treatment. The most meaningful results were obtained from the ascending colon, where a significant effect of the treatment was observed, suggesting that during the exposure to mycotoxins, the pathways involved in cell proliferation and survival were disordered. Changes in miR expression in the liver and the descending colon of the treated gilts were smaller, and were associated more with treatment duration than the exposure to ZEN, DON, or ZEN+DON. Further research should focus on identification of genes whose expression is regulated by these aberrantly expressed miRs. This should facilitate understanding of the miRNA-regulated biological effects of mycotoxins

Preliminary evaluation of mutagenic activity of two amino derivatives of cyclopenta[c]phenanthrene

The mutagenicity of two, newly synthesized amino-derivatives of cyclopenta[c]phenanthrene (CP[c]Ph) was investigated in the Ames test using TA98 and TA100 histidine dependent Salmonella typhimurium strains. Neither of the examined compounds showed mutagenic activity without metabolic activation. The incorporation of an activation system caused high mutagenicity of CP[c]Ph derivatives in both S. typhimurium strains. The results are compared with the previous data on the mutagenic activity of unsubstituted CP[c]Ph and possible mechanisms of activation are discussed