Calcareous corpuscles

Nieland, M. L, Von Brand, T. Electron microscopy of cestode calcareous corpuscle formation. Expl. Parasit 24, 279 (1969)... 

Table 4.4. Phosphate content (% fresh body wt) of calcareous corpuscles isolated from different cestodes. (Data from von Brand et al., 1969)...

Many species of cestodes, especially the larvae, contain large numbers of curious concretions, termed calcareous corpuscles, made up of an organic base together with inorganic material. They are composed of concentric lamellae and vary in size in some species they are very large - 16-32 /xm (Spirometra mansonoides, E. granulosus) - but, in most species, they measure about 12 jam. They have been the subject of a number of studies (36, 135, 351, 385, 386, 594, 796, 912, 913, 914), but their composition, formation and, particularly, function still remain poorly understood. 

Fig. 4.2. In vitro accumulation of15Ca2 + by soft tissues and calcareous corpuscles of larval T. taeniaeformis. c.p.m., counts/min. (After Von Brand Weinbach, 1975.)...

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

It has been suggested by Podesta et al. (650) that ambient C02 levels determine the amount of succinate and lactate excreted by intestinal helminths. A summary of the events which they propose lead to succinate accumulation in H. diminuta is provided in Fig. 5.7. There is considerable release of C02 in the post-prandial intestine of the rat host as the acidic chyme is passed into the duodenum and there is an acidification of worm tissues as the C02 diffuses in. The acidification is countered by worm secretion of H+ and by mobilisation of Ca2 + from the calcareous corpuscles (Chapter 4), thus releasing carbonate. The increased osmolality and greater HC03 concentration activate PEPCK, which favours succinate production over lactate. Succinate, being a dicarboxylic acid, is twice as effective as lactate in metabolic disposal of H+. With a decrease in passage of stomach chyme into the intestine, there would be a decrease in acid stress on the worms, accompanied by a concomitant decrease in tissue HC03 concentrations and osmolality, which would favour lactate production. 

Note The number of cells in a quarter of a section of each of 10 plerocercoids was counted. The percentages of flame cells associated with the calcareous corpuscles were determined from separate sections. The plerocercoids were treated for 5h with colchicine at 38°C. 

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. 

Structure, formation, and functions of calcareous corpuscles in Hymenolepis microstoma. Zeitschrift fur Parasitenkunde, 53 159-69. 

Von Brand, T. Nylen, M. U. (1970). Organic matrix of cestode calcareous corpuscle. Experimental Parasitology, 28 566-76. 

Von Brand, T., Nylen, M. U., Martin, G. N., Churchwell, F. K. Stites, E. (1969). Cestode calcareous corpuscles phosphate relationships, crystallization patterns, and variations in size and shape. Experimental Parasitology, 25 291-310. 

Von Brand, T. Weinbach, E. C. (1975). Incorporation of calcium into the soft tissues and calcareous corpuscles of larval Taenia taeniaeformis. Zeitschrift fur Parasitenkunde, 48 53-63. 

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