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Ribosomal RNA Processing Sites
Published in S. K. Dutta, DNA Systematics, 2019
Robert J. Crouch, Jean-Pierre Bachellerie
Intron sequences have been determined for two other lower eukaryotes, Physarum45 and Chlamydomonas.46 There appears to be little homology in sequence to Tetrahymena introns. Nomiyama et al.45 have pointed out that in each instance, a U at the 5′ junction joins to a G at the 3′ junction. The significance of this “rule” remains unknown. The relationship between Tetrahymena rRNA genes and mitochondrial mRNA genes suggests that splicing of rRNA introns may be related more to mRNA metabolism than to rRNA processing. Indeed, not all species of Tetrahymena have interrupted rRNA genes.
Metabolism of Phosphonates
Published in Richard L. Hilderbrand, The Role of Phosphonates in Living Systems, 2018
The free-living ciliate Tetrahymena pyriformis has been the organism of choice for most of the detailed studies on phosphonate synthesis because of its high phosphonate content (13% of the total phosphorus of the organism) and its ease of cultivation.29 Different strains of Tetrahymena have been used by different investigators but the results appear to be comparable. The rumen ciliate Entodinium caudatum also incorporates 32Pi into AEP.45
Aeromonas
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
Tetrahymena spp. (T. thermophila and T. pyriformis) are freshwater free-living ciliate protozoa that grow readily in culture media between 12°C and 41°C without a CO2-enriched atmosphere, and thus offer an economical and permissive model to evaluate the virulence is aquatic Aeromonas isolates. Aeromonas isolate is considered virulent when relative survival is >60%, whereas Aeromonas isolate is considered avirulent when relative survival is <40%. Similarly, Aeromonas isolate is regarded as virulent when relative survival of T. thermophila is >40% after coculture with Aeromonas, whereas Aeromonas isolate is classified as avirulent when relative survival of T. thermophila is >50% after coculture with Aeromonas [57]. In addition, highly virulent Aeromonas strains grow well in T. thermophila, causing deformation to and even lysis of T. thermophila, whereas avirulent Aeromonas strains are largely phagocytozed by T. thermophila, causing no obvious damage to T. thermophila [59].
Development of reliable quantitative structure–toxicity relationship models for toxicity prediction of benzene derivatives using semiempirical descriptors
Published in Toxicology Mechanisms and Methods, 2023
Ayushi Singh, Sunil Kumar, Archana Kapoor, Parvin Kumar, Ashwani Kumar
Invertebrates and algae are the important testing endpoint for chemical safety assessment and in silico predictive methods are required to fill the data gap of toxicity toward toxicity endpoints (EC–European Commission Regulation 1999; ECHA. 2008; Valerio 2012). Algae form one of the most significant parts of the food chain of the aquatic environment and are responsible for providing basic nutrition to aquatic organisms. Bioaccumulation of chemicals by algae leads to biomagnification which can cause toxicity to other living organisms including human beings (Seth and Roy 2020). Therefore, it is important to develop predictive models for toxicity toward algae like Scenedesmus obliquus. Its rapid reproduction ability and high sensitivity to pollutants make it an attractive model organism for environmental toxicity determination (Cai et al. 2008). Likewise, Ciliated protozoa, e.g. Tetrahymena pyriformis possess many characteristics which are desirable in a test organism for assessment of environmental risk, e.g. it occurs at the first tropic level and shows early indications of toxicity. It is significantly involved in energy and matter transfer and can be cultured easily. These models can be used to study physiological and metabolic processes for several generations which is very important from a toxicology point of view (Bogaerts et al. 2001).
Ion channels as therapeutic antibody targets
Published in mAbs, 2019
Catherine J. Hutchings, Paul Colussi, Theodore G. Clark
Cilated protozoa devote a large part of their metabolism towards membrane protein production and have expanded gene families for all four of the major classes of membrane transporters, including P-type ATPases, major facilitator superfamily members, ABC transporters and voltage-gated ion channels.75Tetrahymena thermophila, in particular, has been identified as an attractive platform for over-expression of recombinant human ion channels based on the fact that its macronuclear genome encodes approximately three times as many voltage-dependent K+ channels as do human cells.75 Although a complex eukaryote, Tetrahymena shares many of the features of microbial expression hosts, including ease of growth in peptone-based media at scale with relatively short doubling times of 2 to 3 hours.76
Predicting skin sensitization potential of organic compounds based on toxicity enhancement to Tetrahymena pyriformis, fathead minnow, and Daphnia magna
Published in Journal of Immunotoxicology, 2018
Weicheng Zhang, Libao Chen, Lunguang Yao
Toxicity enhancement (Te), previously termed excess toxicity, is widely used to determine whether a compound can elicit reactive toxicity through a comparison with its baseline toxicity (von der Ohe et al. 2005; Schramm et al. 2011). Te = 10 has been proposed as a threshold to discriminate reactive from non-reactive compounds. Similarly, one reasonably assumes that toxicity enhancement can be utilized to discriminate a sensitizer from a non-sensitizer. In the present study, data on the toxicity of 65 compounds to Tetrahymena pyriformis, fathead minnow, and Daphnia magna were compiled and collected, and toxicity enhancements of each in the three biosystems were calculated and applied to predict their sensitization potency. The three selected assays in the different species, toxic endpoints, and exposure durations demonstrated that toxicity enhancement was a reliable parameter that could be used to predict skin sensitization potency and discriminate strong (and extreme) and moderate sensitizers from weak and non-sensitizers.