the purpose of this work is to develop robust and interpretable quantitative structure”activity relationship (qsar) models for assessing the aquatic toxicity of phenols using a combined set of descriptors encompassing the logp and recently developed variables (monconn-z variables). the used dataset consists of 250 chemicals with toxicity data to the ciliate tetrahymena pyriformis. for each comp...

A bioassay technique based upon the respiratory response of Tetrahymena pyriformis to intoxication, which gives results within 10 min, was used to evaluate the quality of a number of effluents from three wastewater treatment plants in the PretoriaJohannesburg area. Toxic activity was detected in both treated and untreated wastewater effluent. The technique was shown to be sufficiently sensitive...

Tetrahymena pyriformis, a freshwater protozoan, is common in aquatic systems. Arsenic detoxification through biotransformation by T. pyriformis is important but poorly understood. Arsenic metabolic pathways (including cellular accumulation, effluxion, biomethylation, and volatilization) of T. pyriformis were investigated at various phosphate concentrations. The total intracellular As concentrat...

In a preceding publication a method was reported by which fragments of the nuclear envelopes of Tetrahymena pyriformis could be isolated (10). When macronuclear envelopes were isolated from exponentially growing cultures of the amicronucleate Tetrahymena pyriformis strain GL, two types of envelope pieces were observed which differed markedly in the structure of their pore complexes. Type A cont...

The sensitivity of protozoa, and particularly ciliated protozoa, to environmental changes suggested a study on the physiological responses arising from exposure to toxic compounds. Tetrahymena pyriformis was used as a test organism in a set of miniaturized assays. The physiological response of this ciliate was assessed in terms of adenosine-5'-triphosphate content and acid phosphatase activity ...

The biosynthesis of ubiquinone-8 from radioactive mevalonate by cultures of Tetrahymena pyriformis is demonstrated. Under normal conditions the incorporation of this radioactive precursor into ubiquinone and the triterpenoid alcohol tetrahymanol reflects the amounts of these two compounds in the cell. Growth of T. pyriformis in the presence of cholesterol results in a complete inhibition of inc...

Cyclopropane fatty acids are readily metabolized by whole cells of Tetrahymena pyriformis when the fatty acids are presented either as components of intact Escherichia coli cells or as free fatty acids added to the medium. cis-ll,lZ[methylene-14C]Methyleneoctadecanoic acid was degraded with the production of 14COz by whole T. pyriformis cells or a particulate fraction derived from them. In the ...

The cellular site of synthesis of ribosomal RNA in Tetrahymena pyriformis was studied by analyzing the purified nuclear and cytoplasmic RNA from cells pulse labeled with uridine-(3)H. The results of studies using zonal centrifugation in sucrose density gradients show that the ribosomal RNA is synthesized in the nucleus as a large precursor molecule sedimenting at 35S. The 35S molecule undergoes...

Tetrahymena geleii (S) (Colpidium camp&m) is a ciliated protozoan which has been shown to be capable of synthesizing lipides from protein at an unusually high rate (1, 2). The next obvious step in studies concerned with the metabolism of this organism, therefore, seemed to be a search for the compound, or compounds, serving as precursor of the lipide material. Acetate is known to play a key r&e...