Mesocestoides

Hrckova, G., Velebny, S., Halton, D.W., Day, T.A. and Maule, A.G. (2004) Pharmacological characterization of neuropeptide F (NPF)-induced effects on the motility of Mesocestoides corti (syn. Mesocestoides vogae) larvae. International Journal for Parasitology 34, 83-93. 

Brownlee, D.J.A. and Fairweather, I. (1996) Immunocytochemical localization of glutamate-like immunore-activity within the nervous system of the cestode, Mesocestoides cord and the trematode, Fasciola... 

Terenina, N.B., Reuter, M. and Gustafsson, M.K. (1 999) An experimental, NADPH-diaphorase histochemical and immunocytochemical study of Mesocestoides vogae tetrathyridia. International Journal for Parasitology 29, 787-793. 

A feature of the research carried out on the physiology of the group is the relatively small number of species investigated - most experiments being carried out on Hymenolepis spp., Taenia spp., Moniezia spp., Echinococcus spp. and Mesocestoides spp. amongst the Cyclophyllidea, and various species of Diphyllobothriidae amongst the Pseudophyllidea. 

Fig. 2.8. Nervous system of the tetrathyridium larva of Mesocestoides sp. based on histochemical (for cholinesterase) and histological techniques. (After Hart, 1967.)...

Representative species investigated by these and other techniques such as TEM include the following Dipylidium caninum (755, 756), Diphyllobothrium dendriticum (277,280-283), Echinococcus granulosus (570), Hymenolepis diminuta (462,966), H. microstoma (936, 937, 941, 943), H. nana (202, 206, 966), Mesocestoides sp. (304),... 

As indicated above, the fact that oxygen is consumed in vitro does not imply that oxygen is utilised in vivo, unless evidence is presented that a similar level of oxygen is available in vivo. Some species (Spirometra mansonoides, Mesocestoides corti, Hymenolepis nana, H. diminuta) can be successfully cultured under strict anaerobic conditions, whereas others (H. microstoma, T. crassiceps, Echinococcus sp.) thrive best under air (796 Chapter 10). The significance of oxidative processes in the energy balance of cestodes is discussed in Chapter 5. 

Mesocestoides corti concentrate a variety of cations - chromium, copper, gallium, indium, thallium, zinc and zirconium - into calcareous corpuscles in vitro (36). 

Some useful, general studies on intermediary metabolism include those on Monieziaexpansa (59-61,664) H. diminuta (400,531,590,612,667) H. microstoma (665, 666) Echinococcus spp. (488, 498, 500) Mesocestoides corti (399) Cotugnia digonopora (618, 619) Schistocephalus solidus (406) and Ligula intestinalis (502). 

Mesocestoides corti pyruvate, malate Lactate, succinate, Similar to aerobic with... 

It has been purified (445) and shares some properties in common with malic enzymes from mammals and birds in being NADP-dependent, heat-stable and able to decarboxylate oxaloacetate. The malic enzyme of H. microstoma also has a marked specificity for NADP (216), contrasting with that of Spirometra mansonoides, which appears to be both NAD- and NADP-linked (220). Malic enzyme has been demonstrated in a range of other cestodes including Mesocestoides corti (399), Schistocephalus solidus (406), Moniezia expansa (60), Echinococcus spp. (500) and L. intestinalis (502). 

Krebs cycle intermediates (Table 5.12) and/or enzymes (Table 5.13). Nevertheless, certain key enzymes, especially aconitase and isocitrate dehydrogenase, are very low in activity or are undetectable in species such as H. diminuta, whereas only very small amounts of 14C02, a characteristic end-product of the TCA cycle, were liberated in vitro from [14C]glucose by the tetrathyridia of Mesocestoides corti (399) and adults of Cotugnia digonopora (618). The classical TCA cycle is, therefore, unlikely to function to any significant extent in these cestodes. 

Contrasting results have also been obtained with different species of Mesocestoides. In M. corti, the chief factors inducing strobilar differentiation in vitro appear to be anaerobic conditions (Fig. 10.12, p. 280) and a pH greater than 7.4 (606,607,806). Yet in M. lineatus, the presence of trypsin in the culture media is required for sexual differentiation (382). These phenomena are discussed in further detail in Chapter 10. Whatever the nature of the stimulus which initiates sexual differentiation, there is now strong experimental evidence that it operates via the neurosecretory system. It was speculated, many years ago, that in E. granulosus, the contact stimulus operated via a neurosecretion which in turn induced the release of a strobilisation organiser (796). 

In the cyclophyllidean Mesocestoides corti, uniquely, an asexual development pattern occurs in the definitive host intestine. Both the recently ingested larva (a tetrathyridium) and the adult worm are capable of undergoing asexual multiplication. This is illustrated dramatically by an experiment in which 2000 tetrathyridia were fed to a dog and 45 days later some 15 000 worms were recovered on autopsy (739). This unusual development was first shown by Eckert et al. (192) and has since been studied by a number of workers (383, 607, 739, 871, 907). 

Fig. 9.12. Mesocestoides corti simplified diagram of the asexual and sexual processes occurring in the intestine of the definitive host (cat/dog). (After Smyth, 1987Z>.)...

Many cyclophyllidean larvae will survive in quite simple media, such as balanced saline plus glucose - provided sterility is maintained - for long periods, without undergoing further development. Early work (reviewed 198, 796,854,855,905), which was rather uncritical and empirical, will not be discussed further here. The major advances have been made using various species of the genera Hymenolepis, Echinococcus, Mesocestoides and Taenia as experimental models. 

Mesocestoides spp. culture of asexual (tetrathyridia) and sexual (strobilar) stages... 

Fig. 10.11. Mesocestoides corti. Diagrammatic representation of the stages of sexual differentiation during development of a tetrathyridium to an adult worm in vitro. (Reprinted with permission from International Journalfor Parasitology, 12, Barrett, N. J., Smyth, J. D. Ong, S. J., Spontaneous sexual differentiation of Mesocestoides corti tetrathyridia in vitro, 1982, Pergamon Journals Ltd.)...

Most work has centred on cyclophyllidean species whose larvae develop in mammals. Few studies have been made on the other cestode orders, such as the Pseudophyllidea whose larvae develop in lower vertebrates, especially fish, amphibia and reptilia. Apart from the H. nana/rodent system, discussed earlier, the most studied species have been those which are either readily maintained in laboratory animals or are of medical, veterinary or economic importance, i.e. Echinococcus granulosus, E. multilocularis, Mesocestoides corti, Taenia crassiceps, T. hydatigena, T. multiceps, T. ovis, T. saginata and T. solium. The account given here has been restricted largely to these species. 

Baldwin, J. L., Berntzen, A. K. Brown, B. W. (1978). Mesocestoides cord cation concentration in calcareous corpuscles of tetrathyridia grown in vitro. Experimental Parasitology, 44 190-6. 

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