Assessment of the mutagenicity of fractions from s-triazine-treated Zea mays

A water-soluble extract from maize plants exposed to 3 s-triazine herbicides (atrazine, simazine and cyanazine) has been shown to be mutagenic in strain TA100 of Salmonella. No mutagenic activity was observed in any control plant extracts using either water or a variety of organic solvents. Gel permeation studies of the extracts suggest that the mutagen(s) are small molecules (less than 1000 MW). HPLC fractionation suggests that the mutagens formed from each of the 3 herbicides are similar in polarity and water solubility, eluting in a 50/50 water:methanol fraction. Approximately 89% of 14C-labeled HPLC chromatographable metabolites of atrazine were also associated with this fraction, suggesting a close chemical link between a labeled but unidentified metabolite and the mutagenic activity.     

1986 Survey of genetic toxicology testing in industry,government contract,and academic laboratories

Results of the 1986 Genetic Toxicology Association's survey of industrial, government, contract, and academic laboratories on the status of several assays in genetic toxicology are presented below. 1. The most commonly used assay was the Salmonella typhimurium/mammalian microsomal (Ames) assay, which was used by 83% of all respondents. 2. The next five (5) most commonly used assays were in vitro cytogenetics (72%), in vivo cytogenetics (59%), CHO HGPRT gene mutation (55%), the micronucleus assay (53%), and L517BY gene mutation (45%). 3. The assay showing the greatest percentage increase in routine use was the micronucleus assay which went from 14% in 1984 to 34% in 1986, an increase of 20%. 4. Other assays which increased in routine use were CHO HGPRT mutation (+18%); in vitro cytogenetics (+14%); L5178Y gene mutation (+9%), and the Ames assay (+5%). 5. Routine use of in vitro UDS assays declined by 6%; use of in vitro SCE assays declined by 12%. 6. There was no change in the rate of routine use of in vivo cytogenetics or in vivo SCE assays. 7. Assays routinely performed on contract included the Salmonella assay, CHO HGPRT gene mutation, in vitro cytogenetics, in vitro UDS, in vivo cytogenetics, the micronucleus assay, L5178Y gene mutation, and the Drosophila sex-linked recessive lethal assay. 8. Four assays were being developed by five or more laboratories. These included in vitro SCE (8); the micronucleus assay (7); in vivo SCE (6); and DNA adduct formation (5). 9. A total of 17 assays had been abandoned by one or more laboratories. However, since no assay had been given up by more than three laboratories no conclusions can be drawn about the overall robustness of any of the assays on the survey form.     

Hydrogen sulfide induces direct radical-associated DNA damage

Hydrogen sulfide (H(2)S) is produced by indigenous sulfate-reducing bacteria in the large intestine and represents an environmental insult to the colonic epithelium. Clinical studies have linked the presence of either sulfate-reducing bacteria or H(2)S in the colon with chronic disorders such as ulcerative colitis and colorectal cancer, although at this point, the evidence is circumstantial and underlying mechanisms remain undefined. We showed previously that sulfide at concentrations similar to those found in the human colon induced genomic DNA damage in mammalian cells. The present study addressed the nature of the DNA damage by determining if sulfide is directly genotoxic or if genotoxicity requires cellular metabolism. We also questioned if sulfide genotoxicity is mediated by free radicals and if DNA base oxidation is involved. Naked nuclei from untreated Chinese hamster ovary cells were treated with sulfide; DNA damage was induced by concentrations as low as 1 micromol/L. This damage was effectively quenched by cotreatment with butylhydroxyanisole. Furthermore, sulfide treatment increased the number of oxidized bases recognized by formamidopyrimidine [fapy]-DNA glycosylase. These results confirm the genotoxicity of sulfide and strongly implicate that this genotoxicity is mediated by free radicals. These observations highlight the possible role of sulfide as an environmental insult that, given a predisposing genetic background, may lead to genomic instability or the cumulative mutations characteristic of colorectal cancer.     

Phyllachora species infecting maize and other grass species in the Americas represents a complex of closely related species

The genus Phyllachora contains numerous obligate fungal parasites that produce raised, melanized structures called stromata on their plant hosts referred to as tar spot. Members of this genus are known to infect many grass species but generally do not cause significant damage or defoliation, with the exception of P. maydis which has emerged as an important pathogen of maize throughout the Americas, but the origin of this pathogen remains unknown. To date, species designations for Phyllachora have been based on host associations and morphology, and most species are assumed to be host specific. We assessed the sequence diversity of 186 single stroma isolates collected from 16 hosts representing 15 countries. Samples included both herbarium and contemporary strains that covered a temporal range from 1905 to 2019. These 186 isolates were grouped into five distinct species with strong bootstrap support. We found three closely related, but genetically distinct groups of Phyllachora are capable of infecting maize in the United States, we refer to these as the P. maydis species complex. Based on herbarium specimens, we hypothesize that these three groups in the P. maydis species complex originated from Central America, Mexico, and the Caribbean. Although two of these groups were only found on maize, the third and largest group contained contemporary strains found on maize and other grass hosts, as well as herbarium specimens from maize and other grasses that include 10 species of Phyllachora. The herbarium specimens were previously identified based on morphology and host association. This work represents the first attempt at molecular characterization of Phyllachora species infecting grass hosts and indicates some Phyllachora species can infect a broad range of host species and there may be significant synonymy in the Phyllachora genus.     

Antimicrobial egg cleaning by the fringed darter (Perciformes: Percidae: Etheostoma crossopterum): implications of a novel component of parental care in fishes

Broad-spectrum antimicrobial compounds have recently been identified in the epidermal mucus of fishes and probably serve as a first line of defence against microbial pathogens. Because of the ubiquitous nature of fungi and bacteria in aquatic systems, defence against these pathogens should be required throughout the lifespan of fishes, including the egg stage. We conducted experiments on Etheostoma crossopterum (Percidae: Catonotus), the fringed darter, to determine if the presence of a guarding male inhibits microbial colonization of eggs. Based on results from a combination of in-stream experiments, in vitro microbial assays, and morphological characteristics and behaviour of breeding males, we propose that antimicrobial egg cleaning by the guarding male is an effective component of parental care in these fish. Although innate antimicrobial compounds have been identified in a variety of organisms ranging from insects to vertebrates, integration of these compounds into a species's reproductive life history has been identified only in a small number of insect species. The results from this study not only indicate that E. crossopterum males provide a novel form of vertebrate parental care, but also have implications regarding the evolution of parental care in fishes and transitional evolutionary stages from no parental care to male parental care.     

Regulation of murine airway surface liquid volume by CFTR and Ca2+-activated Cl- conductances

Two Cl(-) conductances have been described in the apical membrane of both human and murine proximal airway epithelia that are thought to play predominant roles in airway hydration: (1) CFTR, which is cAMP regulated and (2) the Ca(2+)-activated Cl(-) conductance (CaCC) whose molecular identity is uncertain. In addition to second messenger regulation, cross talk between these two channels may also exist and, whereas CFTR is absent or defective in cystic fibrosis (CF) airways, CaCC is preserved, and may even be up-regulated. Increased CaCC activity in CF airways is controversial. Hence, we have investigated the effects of CFTR on CaCC activity and have also assessed the relative contributions of these two conductances to airway surface liquid (ASL) height (volume) in murine tracheal epithelia. We find that CaCC is up-regulated in intact murine CF tracheal epithelia, which leads to an increase in UTP-mediated Cl(-)/volume secretion. This up-regulation is dependent on cell polarity and is lost in nonpolarized epithelia. We find no role for an increased electrical driving force in CaCC up-regulation but do find an increased Ca(2+) signal in response to mucosal nucleotides that may contribute to the increased Cl(-)/volume secretion seen in intact epithelia. CFTR plays a critical role in maintaining ASL height under basal conditions and accordingly, ASL height is reduced in CF epithelia. In contrast, CaCC does not appear to significantly affect basal ASL height, but does appear to be important in regulating ASL height in response to released agonists (e.g., mucosal nucleotides). We conclude that both CaCC and the Ca(2+) signal are increased in CF airway epithelia, and that they contribute to acute but not basal regulation of ASL height.     

Representing genetic sequence data for pharmacogenomics: an evolutionary approach using ontological and relational models

MOTIVATION: The information model chosen to store biological data affects the types of queries possible, database performance, and difficulty in updating that information model. Genetic sequence data for pharmacogenetics studies can be complex, and the best information model to use may change over time. As experimental and analytical methods change, and as biological knowledge advances, the data storage requirements and types of queries needed may also change. RESULTS: We developed a model for genetic sequence and polymorphism data, and used XML Schema to specify the elements and attributes required for this model. We implemented this model as an ontology in a frame-based representation and as a relational model in a database system. We collected genetic data from two pharmacogenetics resequencing studies, and formulated queries useful for analysing these data. We compared the ontology and relational models in terms of query complexity, performance, and difficulty in changing the information model. Our results demonstrate benefits of evolving the schema for storing pharmacogenetics data: ontologies perform well in early design stages as the information model changes rapidly and simplify query formulation, while relational models offer improved query speed once the information model and types of queries needed stabilize.     

Microelectrode Guided Implantation of Electrodes into the Subthalamic Nucleus of Rats for Long-term Deep Brain Stimulation

Deep brain stimulation (DBS) is a widely used and effective therapy for several neurologic disorders, such as idiopathic Parkinson’s disease, dystonia or tremor. DBS is based on the delivery of electrical stimuli to specific deep anatomic structures of the central nervous system. However, the mechanisms underlying the effect of DBS remain enigmatic. This has led to an interest in investigating the impact of DBS in animal models, especially in rats. As DBS is a long-term therapy, research should be focused on molecular-genetic changes of neural circuits that occur several weeks after DBS. Long-term DBS in rats is challenging because the rats move around in their cage, which causes problems in keeping in place the wire leading from the head of the animal to the stimulator. Furthermore, target structures for stimulation in the rat brain are small and therefore electrodes cannot easily be placed at the required position. Thus, a set-up for long-lasting stimulation of rats using platinum/iridium electrodes with an impedance of about 1 MΩ was developed for this study. An electrode with these specifications allows for not only adequate stimulation but also recording of deep brain structures to identify the target area for DBS. In our set-up, an electrode with a plug for the wire was embedded in dental cement with four anchoring screws secured onto the skull. The wire from the plug to the stimulator was protected by a stainless-steel spring. A swivel was connected to the circuit to prevent the wire from becoming tangled. Overall, this stimulation set-up offers a high degree of free mobility for the rat and enables the head plug, as well as the wire connection between the plug and the stimulator, to retain long-lasting strength.