Exposure and Multiple Lines of Evidence Assessment of Risk for PCBs Found in the Diets of Passerine Birds at the Kalamazoo River Superfund Site,Michigan

Dietary exposures of passerine birds at the Kalamazoo River, Michigan, were examined due to the presence of polychlorinated biphenyls (PCBs) in the terrestrial and aquatic food webs. Average potential daily doses in diets were 6- to 29-fold and 16- to 35-fold greater at a contaminated location than at a reference location for PCB exposures quantified as total PCBs and 2,3,7,8–tetrachlorodibenzo-p-dioxin equivalents (TEQs), respectively. Birds with diets comprised of primarily aquatic insects had greater dietary exposure than birds with diets of primarily terrestrial insects. Risk associated with dietary exposure varied with the selection of the threshold for effects including hazard quotients, which exceeded 1 in instances where the most conservative toxicity reference values were utilized. Risk based on concentrations of PCBs in the tissues indicated little risk to avian species, and co-located studies evaluating reproductive health did not suggest that observed incidences of diminished reproductive success were related to PCB exposure. Measures of risk based on comparison to toxicity reference values (TRVs) were consistent with direct measures of ecologically relevant endpoints of reproductive fitness, but uncertainty exists in the selection of threshold values for effects in these species especially based on TEQs. This is largely due to the absence of species-specific, dose-response relationships. Therefore, the best estimate of risk is through the application of multiple lines of evidence.     

Molecular details of Itk activation by prolyl isomerization and phospholigand binding: the NMR structure of the Itk SH2 domain bound to a phosphopeptide

The Src homology 2 (SH2) domain of interleukin-2 tyrosine kinase (Itk) is a critical component of the regulatory apparatus controlling the activity of this immunologically important enzyme. To gain insight into the structural features associated with the activated form of Itk, we have solved the NMR structure of the SH2 domain bound to a phosphotyrosine-containing peptide (pY) and analyzed changes in trans-hydrogen bond scalar couplings ((3h)J(NC')) that result from pY binding. Isomerization of a single prolyl imide bond in this domain is responsible for simultaneous existence of two distinct SH2 conformers. Prolyl isomerization directs ligand recognition: the trans conformer preferentially binds pY. The structure of the SH2/pY complex provides insight into the ligand specificity; the BG loop in the ligand-free trans SH2 conformer is pre-arranged for optimal contacts with the pY+3 residue of the ligand. Analysis of (3h)J(NC') couplings arising from hydrogen bonds has revealed propagation of structural changes from the pY binding pocket to the CD loop containing conformationally heterogeneous proline as well as to the alphaB helix, on the opposite site of the domain. These findings offer a structural framework for understanding the roles of prolyl isomerization and pY binding in Itk regulation.     

The effects of paradoxical sleep deprivation on estrous cycles of the female rats

The present purpose was to examine how sleep deprivation affects the estrous cycle of the female rat. Paradoxical sleep-deprived (PSD) adult female Wistar rats were compared to home-cage control (CTRL) on their estrous cyclicity. Forty-four PSD and forty-four CTRL female rats were distributed into 4 subgroups of 11 animals each according to the phase of estrous cycle and were subjected to sleep deprivation for 96 h by the multiple platform technique. After PSD period, vaginal estrous cycles were taken for an additional 9 days. Animals that were submitted to PSD in diestrus phase (PSD-diestrus) had their estrous cycles disrupted during the recovery period by showing a constant diestrus during the first week. As for hormone alterations, progesterone concentrations were statistically higher in PSD-diestrus compared to respective phase control and to PSD-proestrus and PSD-estrus rats while CTRL-metestrus had higher levels than CTRL-proestrus and estrus groups. Testosterone was significantly decreased in PSD-estrus in relation to PSD-proestrus and PSD-diestrus groups and was lower in CTRL-diestrus rats than in home-cage rats in proestrus. In addition, PSD-diestrus phase exhibited higher concentrations of corticosterone and lower estrogen than the respective control rats. These data indicate that PSD may modulate the ovarian hormone release through alterations in hormonal-neurochemical mechanisms.     

Protein phosphatase activity is necessary for myofibrillogenesis

During myofibrillogenesis, myosin light-chain kinase (MLCK) phosphorylates the regulatory light chain (RLC) of myosin II, enabling patterned assembly of myosin thick filaments. A protein phosphatase (PP) has been shown to mediate RLC dephosphorylation in adult smooth and striated muscle. A role for PP activity in regulating myofibrillogenesis during embryonic development, however, has not been investigated. Tautomycin (TM) was used to inhibit both PP1 and PP2A activities, whereas okadaic acid (OA) and fostriecin (FOS) were used to inhibit PP2A. TM affected both actin and myosin assembly at 5nM; the IC50 value was 20 and 8.5nM, respectively. In contrast, OA applied at 10 times above its reported Ki for PP2A caused no significant disruption. There was also no disruption when FOS was applied at a concentration 30 times above its reported Ki for PP2A. Thus, our results suggest a primary role for PP1 isoforms during myofibrillogenesis. Although rho kinase (RK) regulates PP activity in embryonic smooth and cardiac muscle, application of the RK inhibitor Y27632 did not affect actin or myosin assembly in skeletal myocytes. Collectively, our pharmacological results suggest that PP1 is involved in dynamic regulation of RLC phosphorylation. To specifically test involvement of the myosin-targeted isoform (PP1M), we used a morpholino antisense approach to knock down the myosin targeting (M) subunit of PP1. Embryos injected with morpholino targeted to the 110-kDa M targeting subunit had fewer somites, and myosin organization was significantly perturbed. The combined pharmacological and molecular results suggest a dynamic equilibrium between MLCK and PP1M activities is required for proper myofibrillogenesis.     

The Mycobacterium tuberculosis Ku C-terminus is a multi-purpose arm for binding DNA and LigD and stimulating ligation

Bacterial non-homologous end joining requires the ligase, LigD and Ku. Ku finds the break site, recruits LigD, and then assists LigD to seal the phosphodiester backbone. Bacterial Ku contains a core domain conserved with eukaryotes but has a unique C-terminus that can be divided into a minimal C-terminal region that is conserved and an extended C-terminal region that varies in sequence and length between species. Here, we examine the role of Mycobacterium tuberculosis Ku C-terminal variants, where we removed either the extended or entire C-terminus to investigate the effects on Ku–DNA binding, rates of Ku-stimulated ligation, and binding affinity of a direct Ku–LigD interaction. We find that the extended C-terminus limits DNA binding and identify key amino acids that contribute to this effect through alanine-scanning mutagenesis. The minimal C-terminus is sufficient to stimulate ligation of double-stranded DNA, but the Ku core domain also contributes to stimulating ligation. We further show that wildtype Ku and the Ku core domain alone directly bind both ligase and polymerase domains of LigD. Our results suggest that Ku-stimulated ligation involves direct interactions between the Ku core domain and the LigD ligase domain, in addition to the extended Ku C-terminus and the LigD polymerase domain.     

No effect of mobile phone-like RF exposure on patients with atopic dermatitis

This study investigates the effect of exposure to a mobile phone-like radiofrequency (RF) electromagnetic field on people with atopic dermatitis (AD). Fifteen subjects with AD were recruited and matched with 15 controls without AD. The subjects were exposed for 30 min to an RF field at 1 W/kg via an indoor base station antenna attached to a 900 MHz GSM mobile phone. Blood samples for ELISA analysis of the concentration of substance P (SP), tumor necrosis factor receptor 1 (TNF R1), and brain derived neurotrophic factor (BDNF) in serum were drawn before and after the provocation (exposure/sham). Baseline heart rate and heart rate variability, local blood flow, and electrodermal activity were also recorded. No significant differences between the subject groups were found for baseline neurophysiological data. The cases displayed a serum concentration of TNF R1 significantly higher than the control subjects and a significantly lower serum concentration of BDNF in the baseline condition. For SP there was no difference between groups. However, no effects related to RF exposure condition were encountered for any of the measured substances. As to symptoms, a possible correlation with exposure could not be evaluated, due to too few symptom reports. The result of the study does not support the hypothesis of an effect of mobile phone-like RF exposure on serum levels of SP, TNF R1, and BDNF in persons with AD.     

Skin mucus proteins of lumpsucker (Cyclopterus lumpus)

Fish skin mucus serves as a first line of defense against pathogens and external stressors. In this study the proteomic profile of lumpsucker skin mucus was characterized using 2D gels coupled with tandem mass spectrometry. Mucosal proteins were identified by homology searches across the databases SwissProt, NCBInr and vertebrate EST. The identified proteins were clustered into ten groups based on their gene ontology biological process in PANTHER (www.patherdb.org). Calmodulin, cystatin-B, histone H2B, peroxiredoxin1, apolipoprotein A1, natterin-2, 14-3-3 protein, alfa enolase, pentraxin, warm temperature acclimation 65 kDa (WAP65kDa) and heat shock proteins were identified. Several of the proteins are known to be involved in immune and/or stress responses. Proteomic profile established in this study could be a benchmark for differential proteomics studies.     

G100R mutation within 4070A murine leukemia virus Env increases virus receptor binding,kinetics of entry,and viral transduction efficiency

Passage of 4070A murine leukemia virus (MuLV) in D17 cells resulted in a G-to-R change at position 100 within the VRA of the envelope protein (Env). Compared with 4070A MuLV, virus with the G100R Env displayed enhanced binding on target cells, internalized the virus more rapidly, and increased the overall viral titer in multiple cell types. This provides a direct correlation between binding strength and efficiency of viral entry. Deletion of a His residue at the SU N terminus eliminated the transduction efficiency by the G100R virus, suggesting that the G100R virus maintains the regulatory characteristics of 4070A viral entry. The improved transduction efficiency of G100R Env would be an asset for gene delivery systems.     

Micronuclei frequency in children exposed to environmental mutagens: a review

Cytogenetic monitoring has been traditionally used for the surveillance of populations exposed to genotoxic agents. In recent years sensitivity problems emerged in surveys of populations exposed to low levels of mutagens, and therefore alternative approaches have been explored. Biomonitoring studies in children are a promising field, since because of evident differences in the uptake, metabolism, distribution and excretion of mutagens this population seems to be more susceptible than adults. Further, the effect of major confounders such as cigarettes smoking, occupation, life-style, and dietary factors plays a minor role. Among cytogenetic assays, the micronucleus assay (MN) has several advantages and is increasingly used. A review was then carried out to synthesize the published data on the occurrence of MN in children and adolescents (age range 0-18 years), and to assess the impact of genotoxic exposure on MN frequency. Overall, 20 papers from international literature and 8 Russian papers were included. An effect of age was found within this age range, while the influence of gender on MN frequency was irrelevant. These results were confirmed by the re-analysis of data for 448 children selected from the HUMN database. An effect of chronic and infectious diseases on MN levels has been reported by various authors. Most studies describing the effect of exposure to genotoxic agents (ionizing radiation, chemicals, drugs, environmental tobacco smoke) found an increase of MN in exposed children. The limited number of published papers indicates that the conduct of properly designed studies on the effect of environmental pollutants in children may be difficult. This review confirmed the usefulness of MN assay in biomonitoring studies conducted in children, revealing that in many circumstances investigating children increases the sensitivity of the study, even with low dose exposures.