Microbialite response to an anthropogenic salinity gradient in Great Salt Lake, Utah.

A railroad causeway across Great Salt Lake, Utah (GSL), has restricted water flow since its construction in 1959, resulting in a more saline North Arm (NA; 24%-31% salinity) and a less saline South Arm (SA; 11%-14% salinity). Here, we characterized microbial carbonates collected from the SA and the NA to evaluate the effect of increased salinity on community composition and abundance and to determine whether the communities present in the NA are still actively precipitating carbonate or if they are remnant features from prior to causeway construction. SSU rRNA gene abundances associated with the NA microbialite were three orders of magnitude lower than those associated with the SA microbialite, indicating that the latter community is more productive. SSU rRNA gene sequencing and functional gene microarray analyses indicated that SA and NA microbialite communities are distinct. In particular, abundant sequences affiliated with photoautotrophic taxa including cyanobacteria and diatoms that may drive carbonate precipitation and thus still actively form microbialites were identified in the SA microbialite; sequences affiliated with photoautotrophic taxa were in low abundance in the NA microbialite. SA and NA microbialites comprise smooth prismatic aragonite crystals. However, the SA microbialite also contained micritic aragonite, which can be formed as a result of biological activity. Collectively, these observations suggest that NA microbialites are likely to be remnant features from prior to causeway construction and indicate a strong decrease in the ability of NA microbialite communities to actively precipitate carbonate minerals. Moreover, the results suggest a role for cyanobacteria and diatoms in carbonate precipitation and microbialite formation in the SA of GSL.

Oncogenic studies with felbamate (2-phenyl-1,3-propanediol dicarbamate).

Felbamate, 2-phenyl-1,3-propanediol dicarbamate, is a novel anticonvulsant that is effective against both chemically and electrically induced seizures in laboratory animals. Oncogenic studies were conducted in mice and rats to establish a preclinical safety profile for this drug. There was an increased incidence of hepatic cell adenoma in male and female mice and in female rats. There was an increased incidence of interstitial cell tumors of the testes in the male rat.

Acute, subchronic, and chronic toxicity studies with felbamate, 2-phenyl-1,3-propanediol dicarbamate.

Felbamate, 2-phenyl-1,3-propanediol dicarbamate, is a novel anticonvulsant that is effective against both chemically and electrically induced seizures in laboratory animals. Acute, subchronic, and chronic studies were conducted in mice, rats, and dogs to establish a preclinical safety profile for this drug. Clinical signs following single intraperitoneal doses included hypoactivity, tremors, decreased muscle tone, ataxia, prostration, and labored breathing. Death was observed after intraperitoneal but not oral administration. A consistent drug-related effect noted in all multiple-dose studies with this compound was decreased body weight and food consumption. The only other consistent change noted in multiple-dose studies with felbamate was an increase in liver weight (relative and absolute) in the rat and dog which was accompanied in some cases by increases in serum enzyme levels. No histopathological changes were observed in the liver that could explain these elevated serum enzyme levels. Based on the results of these studies it was concluded that long-term administration of felbamate in human clinical trials was warranted.

In vivo mutagenicity studies with iodinated glycerol azeo.

Previous studies have shown that iodinated glycerol azeo is positive in a number of in vitro mutagenicity assays including the Ames assay (TA100; TA1535), mouse lymphoma assay, Chinese hamster ovary (cytogenetic) assay and in one in vivo study, the sex-linked-recessive-lethal assay in Drosophila. Prior studies have also shown that the drug is negative in the mouse micronucleus assay. We now report that the drug is also negative for mutagenic activity in a number of other in vivo tests. Single intraperitoneal doses of 25, 125 and 250 mg/kg were without effect in the rat bone marrow chromosomal aberration assay. Single oral doses of 30, 75, 150 and 300 were negative in the rat hepatocyte DNA-repair assay. Single intraperitoneal doses of 30 and 100 mg/kg were without effect in the sister chromatid exchange (SCE) assay in the mouse. Statistically significant effects were seen at 200 and 300 mg/kg in the initial SCE assay and at 300 and 350 mg/kg in the confirmatory SCE assay. The rationale for considering the SCE results to be anomalous and thus not relative to the overall safety evaluation of the drug is presented.

Critique of the toxicology and carcinogenesis studies of iodinated glycerol in F344/N rats and B6C3F1 mice.

Carter-Wallace conducted a detailed audit and evaluation of the data available from the carcinogenicity studies with iodinated glycerol conducted in the B6C3F1 mouse and the F344/N rat by the National Toxicology Program (NTP). We conclude that there is no evidence of carcinogenicity of the compound in either the B6C3F1 mouse or the F344/N rat.

Equilibrium sedimentation of turnip yellow mosaic virus.

Sedimentation equilibrium was achieved with turnip yellow mosaic virus at low speeds (600 rpm) in a magnetic ultracentrifuge. The experiments were carried out in the newly installed constant-speed rotor, equipped with automatic control and an electromagnetic drive. A particle mass of 5.55 x 10(6) daltons was calculated for the virus at vanishing concentrations, in essential agreement with the earlier results using the more tedious procedure with a freely coasting rotor. In order to interpret the observed departure from ideal behavior (nonassociating conditions), preferential interaction experiments were carried out by magnetic densimetry. These showed that a strong Donnan effect exists at pH 7, which contributed > 10(3) times more to the nonideality than did the excluded volume effect. A net negative charge of about 3.5 x 10(3) per particle was estimated at this pH.