Parasitic protozoa

Bacteria are likely precipitants in many other cases including Escherichia coli, Salmonella species, Shigella species, Vibrio cholerae, and Clostridium difficile. The term dysentery has often been used to describe some of these bacterial infections when associated with serious occurrences of bloody diarrhea. Additionally, acute diarrheal conditions can be prompted by parasites-protozoa such as Entamoeba histolytica, Microsporidium, Giardia lamblia, and Cryptosporidium parvum. Most of these infectious agents can be causes of traveler s diarrhea, a common malady alflicting travelers worldwide. It usually occurs during or just after travel subsequent to the ingestion of fecally-contaminated food or water. It has an abrupt onset but usually subsides within 2 to 3 days. 

Other contributions to this book have taken a molecular view of parasitic nematodes, yet molecules make only a rather brief appearance here. This chapter has tried to show that parasitic nematodes are fascinatingly and tantalizingly diverse at a phenotypic level. It has focused particularly on diversity in phenotypes that are apparent in response to environmental conditions within or outside a host. The interaction of parasites with within-host factors is a major current research effort. However, helminth immunology is particularly notable for its inattention to diversity, especially when compared with the immunology of parasitic protozoa (Read and Viney, 1996). Observations of the interaction of host immunity with subsequent development in S. ratti show the potential power of such interactions. It is also clear that a principal mechanism of the action of host immune responses is against nematode fecundity (Stear et al., 1997). This is likely to be a molecularly complex interaction. Understanding this interaction, as well as variation in the interaction is interesting, but could also form the basis of control by transmission-reduction rather than eradication per se. 

Borst, P., Ouellette, M., New mechanisms of drug resistance in parasitic protozoa, Anna. Rev. Microbiol. 1995, 49, 427-460. 

The immune system protects humans and animals from microbial infections by such infectious agents as bacteria, yeasts and fungi, viruses and protozoa. These differ greatly not only in their size but in their structural and molecular properties, as well as in the ways in which they seek to infect our bodies. Some of these pathogens infect bodily fluids, some penetrate tissues and some even survive and multiply within individual host cells. These intracellular pathogens include viruses, some parasitic protozoa (such as Plasmodium, the causative agent of malaria, which infects erythrocytes) and... 

Ottoson J, Hansen A, Bjorlenius B, Norder H, Stenstrom TA (2006) Removal of viruses, parasitic protozoa and microbial indicators in conventional and membrane processes in a wastewater pilot plant. Water Res 40 1449-1457... 

To date, no effective vaccine has been developed for many parasites, notably the malaria-causing parasitic protozoa Plasmodium. One of the major difficulties in such instances is that parasites go through a complex life cycle, often spanning at least two different hosts. 

Radiation effects on parasitic protozoa and helminths are associated with loss of infectivity, loss of pathogenicity, interruption or prevention of completion of life cycle, and death of parasites [10]. 

J. E. Ellis (1994). Coenzyme Q homologs in parasitic protozoa as targets for chemotherapeutic... 

They are especially abundant in many parasitic protozoa and may carry additional glycosyl groups.1863... 

Purine bases from ingested foods, or formed by catabolism of nucleic acids, are able to react with PRPP under the influence of phosphoribosyltransferases.3063 Two such enzymes are known to act on purines. One converts adenine to AMP (Fig. 25-17, step b) and also acts upon 5-aminoimidazole-4-carboxamide. This enzyme may be especially important to parasitic protozoa such as Leishmania, which lack the de novo pathway of purine synthesis (Fig. 25-15).278/306b... 

Trypanosomes and other parasitic protozoa are unable to synthesize purines and must obtain them from their hosts using salvage pathway. Selective inhibition of their HGPRT or of nucleoside hydrolases, which are absent from mammalian cells, are goals of drug development.3273 1 ... 

Kelly, J.M. (1 997) Genetic transformation of parasitic protozoa. Advances in Parasitology 39, 227-270. 

Coppens, I. and Courtoy, P.J. (1996) The mevalonate pathway in parasitic protozoa and helminths. Experimental Parasitology 82, 76-85. 

Protozoa are microscopic animals consisting of single eukaryotic cells and classified on the bases of morphology, means of locomotion, presence or absence of chloroplasts, presence or absence of shells, and ability to form cysts. Several devastating human diseases, including malaria, sleeping sickness, and some kinds of dysentery, are caused by parasitic protozoa. Parasitic protozoa can cause debilitating, even fatal, diseases in livestock and wildlife. 

Hammarton TC, Mottram JC, Doerig C (2003) The cell cycle of parasitic protozoa potential for chemotherapeutic exploitation. Prog Cell Cycle Res 5 91-101... 

Doerig C, Meijer L, Mottram JC (2002) Protein kinases as drug targets in parasitic protozoa. Trends Parasitol 18(8) 366-371... 

Extensive work by Cheah (121, 122, 123, 128, 130), mainly with M. expansa, has shown that large cestodes possess a cytochrome chain which differs from the mammalian system in being branched and possessing multiple terminal oxidases (Fig. 5.11). One branch resembles the classical chain with cytochrome a3 as its terminal oxidase. The terminal oxidase of the alternative pathway, which branches at the level of rhodoquinone or vitamin K, is an o-type cytochrome. Cytochrome o is an autoxidisable b-type cytochrome which is commonly found in micro-organisms, parasitic protozoa and plants. The classical chain constitutes about 20% of the oxidase capacity in cestodes and cytochrome o is quantitatively the major oxidase. Cyanide-insensitive respiration - i.e. where oxygen uptake occurs in the presence of cyanide - is characteristic of most helminths (39). Cytochrome o binds cyanide much less strongly than cytochrome a3, and it seems reasonable, therefore, to equate cyanide-insensitive respiration with the non-classical pathway. 

Some interface phenomena in parasitic protozoa and platyhelminths. Canadian Journal of Zoology, 51 367-77. 

Richards TA, Hirt RP, Williams BAP, Embley TM (2003) Horizontal gene transfer and the evolution of parasitic Protozoa. Protist 154 17-32... 

Mitosomes of Parasitic Protozoa Biology and Evolutionary Significance... 

The physiology of mitosomes appears to be diverse too. Sequence information from the genome projects of parasitic protozoa has revealed the extent... 

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