Assessing the Chronic Aquatic Toxicity of Phthalate Ester Plasticizers

Phthalic acid esters (PAE) are a class of chemicals varying greatly in terms of uses, properties, and toxicity. C1 to C4 PAE are used in non-vinyl commercial products and pharmaceuticals. C8 to C10 PAE are additives imparting flexibility to vinyl resins. The purpose of the present study is to assess chronic effects of PAE on aquatic organisms. Studies show that populations of fish and invertebrates may be adversely affected by exposure to C1 to C4 PAE, but are not adversely affected by exposure to C8 or higher PAE. Secondary endpoints, including molecular, biochemical, and/or histological responses to chemical exposure, do not appear to predict effects related to primary endpoints of survival, growth and development, or reproductive fitness. A previously published risk assessment for C1 to C4 PAE demonstrated low risks in North American and Western European surface waters. Risk assessments conducted by authorities in Europe with di-2-ethylhexyl-, di-isononyl-, and di-isodecyl phthalates have concluded no risks to aquatic organisms due to aqueous solubility constraints, low expected surface water concentrations, and metabolic biotransformation capabilities of aquatic organisms. The present review of chronic aquatic toxicity data, which includes data from studies performed subsequent to the risk assessments, confirms these earlier conclusions.     

Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase

Molecular and Cellular Biochemistry - Within the last few years considerable evidence has accumulated which indicates that changes in HMG-CoA reductase are due primarily, if not solely, to changes...     

Dynamical behavior for population genetics models of differential and difference equations with nonmonotone fitnesses

This paper studies the dynamical behavior of classical 2-dimensional models of continuously and discretely reproducing diploid populations with two alleles at one locus. The phase variables are allele frequency and population density. The genotype fitnesses are not assumed to be monotonically decreasing functions of density. Hence the mean fitness curve is more complicated than in the monotonic case. If genotype fitnesses are only density dependent, results concerning equilibrium stability are obtained similar to those for the monotonic case, and periodic solutions are precluded in the differential equation model. An example with one-hump genotype fitnesses is presented and analyzed.Research supported by funds provided by the USDA-Forest Service, Southeastern Forest Experiment Station, Pioneering (Population Genetics of Forest Trees) Research Unit, Raleigh, North Carolina     

Stable periodic solutions for two species,density dependent coevolution

This paper studies a four dimensional system of time-autonomous ordinary differential equations which models the interaction of two diploid, diallelic populations with overlapping generations. The variables are two population densities and an allele frequency in each of the populations. For single species models, the existence of periodic solutions requires that the genotype fitness functions be both frequency and density dependent. But, for two species exhibiting a predator-prey interaction, two examples are presented where there exists asymptotically stable cycles with fitness functions only density dependent. In the first example, the Hopf bifurcation theorem is used on a two parameter, polynomial vector field. The second example has a Michaelis-Menten or Holling term for the interaction between predator and prey; and, for this example, the existence and uniqueness of limit cycles for a wide range of parameter values has been established in the literature.     

The ‘Oxycythereis’ problem: taxonomy and palaeobiogeography of deep‐sea ostracod genera Pennyella and Rugocythereis

Systematic revision of the globally distributed deep‐sea ostracod genera Pennyella Neale, 1974 and Rugocythereis Dingle, Lord and Boomer, 1990, which have been considered to correspond, at least partially, to nomen nudum but widely used genus name ‘Oxycythereis,’ was conducted to reduce taxonomic uncertainty of these important components of the Modern and fossil deep‐sea ostracod community. Approximately 100 specimens from 18 species were examined, ranging in age from the Cretaceous to the present day. Nine new species are described: Pennyella rexi, Pennyella sanfordae, Pennyella liowae, Pennyella schellenbergi, Pennyella majorani, Pennyella iani, Pennyella ayressi, Rugocythereis melonis and Rugocythereis zarikiani. Emended generic concepts of Pennyella and Rugocythereis are proposed, and the palaeobiogeographical distributions of these two genera are discussed.     

The establishment of mouse embryonic stem cell cultures on 96-well plates for high-throughput screening

Embryonic stem (ES) cells can be valuable for monitoring differentiation processes and for improving applications in basic developmental biology. The application of ES cells can be a useful tool for drug discovery and toxicology. Therefore, we suggest the high-throughput screening (HTS) system based on ES cells in this study. Firstly, we optimized the feeder-free condition and seeding cell number which can maintained for at least 7 days without over-confluency. We analyzed the system by cell viability, proliferation activity, RT-PCR and morphologic/immunohistochemical evaluations. The optimal cell seeding number was 30/well that was maintained the typical colonial morphology over 9 d with 1,000 U/ml LIF in the limited space. The cell in optimized condition expressed ALP, SSEA-1, Oct 4 and Nanog and the genetic expressions showed similar to protein expressions. The cell lineage marker expressions showed faint or none. The cell viability and proliferation activity were increased in time-dependent manner in our optimized HTS system. In conclusion, the novel HTS system using ES cells can by useful for developing models for drug discovery as well as toxicological screening in the near future.