In protozoa

In protozoa this problem is solved by the addition of preexisting oligodeoxynucleotide blocks to the 3 ends of DNA. These blocks are composed of tandemly repeated units of (T2G4)n or (T4G4)n, where n is approximately 50. The enzyme that adds these polymers requires a primer but not a template. These oligonucleotide block polymers are called telomers. Another DNA polymerase,... 

Mast, S. O. Motor responses in unicellular animals, in Protozoa in Biological Research. (Calkins, G.N. and Summers, F.M., eds.), pp. 271-351. New York Columbia Univ. Press 1941... 

Naitoh, Y., Eckert, R. Control of Ciliary Activity in Protozoa, in Cilia and Flagella (Sleigh, M.A., ed.), pp. 305-352. London Academic Press 1974... 

Table 2 gives some of the experimental approaches demonstrating endocytosis of contaminants in Protozoa, and Table 3 summarises the experimental approaches for Metazoa. 

The last class of three major membrane anchors is caused by the modification by a glycophospholipid, glycosylphosphatidylinositol (GPI) (Udenfriend and Kodukula, 1995a Takeda and Kinoshita, 1995). They are observed in many eukaryotes, especially in protozoa and yeasts. Unlike other classes, the GPI-anchored proteins are exposed at the (extracytoplasmic) surface of the plasma membrane. Thus, we can predict the localization at the plasma membrane from the presence of a GPI anchor, although some of them are further incorporated into the cell wall in S. cerevisiae (as described in Section III,K,1). 

The exact action is not fully elucidated. However, bulaquine inhibits protein synthesis in protozoa and indirectly inhibits polymerisation of amino acids by the plasmodia. Treatment prevents emergence of either primary or secondary liver stage para-sitaemia and the disease. 

MEP/DXPpathway. 2-C-methyl-D-erythritol4-phosphate/r-de-oxy-D-xylulose s-phosphate pathway, first reported in the late 1980s, is also known as non-mevalonate pathway or mevalonic acid independent pathway (MEP). This pathway is located in the plastids of plants and in the stmcture known as the api-complexan in protozoa as well as in many bacteria. 

Muller M (1973) Peroxisomes and hydrogenosomes in protozoa. J Histochem Cytochem 21 955-957... 

Piccinni, E. Coppellotti, O. Phosphagens in protozoa - II. Presence of phosphagen kinase in Ochromonas danica. Comp. Biochem. Physiol. B, 62, 287-289 (1979)... 

Contractile Vacuole (pulsating vacuole) A vesicular reservoir in protozoa in which water and waste products collect and are discharged to the outside by means of a contraction of the vacuole. 

In protozoa thymidylate synthase and dihydrofolate reductase exist as a single bifunctional protein. 

Thymidylate synthase requires methylene tetrahydro-folate as a reductant and the reduction of dihydrofolate is also an important part of the process. In protozoa dihydrofolate reductase and thymidylate synthase occur as a singlechain bifunctional enzyme.f As has been pointed out in the main text, such folic acid analogs as methotrexate are among the most useful anticancer drugs. By inhibiting dihydrofolate reductase they deprive thymidylate synthase of an essential substrate. 

Abraham-Peskir JV, Butler RD, Sigee DC. 1997. Seasonal changes in whole-cell metal levels in protozoa of activated sludge. Ecotoxicol Environ Saf 38 272-280. 

Muller M (1980) The hydrogenosome. Symp Soc Gen Microbiol 30 127-142 Muller M (1985) Search for cell organelles in protozoa. J Protozool 32 559-563 Muller M (1992) Energy metabolism of ancestral eukaryotes a hypothesis based on the biochemistry of amitochondriate parasitic protists. BioSystems 28 33-40 Muller M (2003) Energy metabolism. Part I Anaerobic protozoa. In Marr J, Nilsen T, Komuniecki R (eds) Molecular medical parasitology. Academic, London, pp 125-139 Muller M, Hogg JF, de Duve C (1968) Distribution of tricarboxylic acid cyle enzymes andofgly-oxylate cycle enzymes between mitochondria and peroxisomes of Tetrahymena pyriformis. J Biol Chem 243 5385-5395... 

In protozoa and some algae, cation sequestration is one of the functions of acidocalci-some (Docampo and Moreno, 2001 Ruiz et al, 2001a,b). This is an electron-dense acidic organelle, which contains pyrophosphate and PolyP bound with Ca2+ and other cations. Its membrane possesses a number of pumps and exchangers for the uptake and release of these elements. 

PolyP in protozoa was found long ago (Ebel et al., 1958b Mattenheimer, 1958 Janakidevi et al, 1965 Rosenberg, 1966). Its metabolism was studied with the purpose of searching for specific biochemical peculiarities of parasitic representatives of this taxon, which could offer prospects for drug development. 

Caron, D. A. (1991). Evolving role of protozoa in aquatic nutrient cycles. In Protozoa and their Role in Marine Processes (Reid, P. C., Turley, C. M., and Burkfll, P. H., eds.) Springer, Berlin, pp. 387-415. 

Waive, J., and Larsson, U. (1999). Carbon, nitrogen and phosphoms stoichiometry of crustacean zooplankton in the Baltic Sea Implications for nutrient cychng.J. Plankton Res. 21(12), 2309—2321. Weatherby, J. H. (1929). Excretion of nitrogenous substances in protozoa. Physiol. Zool. 2, 375—394. Webb, K. L., and Johannes, R. E. (1967). Studies of the release of dissolved free amino acids hy marine zooplankton. Limnol. Oceanogr. 12, 376—382. 

In protozoa, e. g., Leishmania and Trypanosoma, glycolipids have been identified that possess a GPI anchor (see Chap. 7.4) [74]. Characteristic for Leishmania is lipophosphogly-can [74,75,76,77] which covers the entire surface of the promastigote. The molecule can be divided in four regions, i. e., lipid anchor, core region, repeating units, and cap, the last of which vary in different species. 

The benzeneacetonitrile diclazuril has been used in the treatment of EPM in horses. Its mode of action is not completely understood but it is believed to have efficacy against a plastid-like organelle in protozoa. Oral administration of diclazuril to horses at 5.5mg/kg for 21 days provides CSF concentrations of 100-250ng/ml, which exceed the concentrations required to inhibit 95% of the proliferation of S. neurona in tissue culture (Dirikolu et al 1999). This compound is currently undergoing safety and efficacy trials in the USA for the treatment of EPM in horses. 

Single cells may deposit CaCOs extracellularly. This occurs in the formation of the test in protozoa (Pautard, 1970) and the spicules of calcareous sponges (Jones, 1970). Single cells also have the capacity to form portions or entire skeletons of echinoderm larvae in vitro (Okazaki, 1975) and cells which do not form distinct epithelia regenerate spines of echinoderms extracellularly (Heatfield and Travis, 1972). These results suggest the possibility that cells which are not in an epithelial layer may also deposit the meshwork of the echinoderm test and spines extracellularly. 

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