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272 H. PLATTNER ET AL» activity (Fig. 5) at the preformed exocytotic fusion sites of paramecia (P 1 a 11 n e r et al. 1978). This activity was absent from exocytotically inactive mutations devoid of "rosettes" and simultaneously of "connecting material" (P 1 a 11 n e r et al. 1980); see Table 1. Some differences were also found biochemically, when pellicles were isolated from exocytosis-capable and -incapable strains and assayed by spectral photometric tests for their Ca 2+ -ATPase activity (B i 1 i n s k i et al. 1981 b). All this opens up several possibilities: The ATPase could represent a Ca 2 +-pump (keeping the local Ca 2+ concentration low and thus avoiding membrane fusion in the untriggered state; see also B e i s s o n et al. 1980), a site of protein phosphorylation (as in other exocytotic systems, like synaptosomes), a Ca 2+ -channel (if combined with a pump, as in other systems, like sarcoplasmic reticulum) or it could indicate the presence of contractile elements of the actomyosin type. Since exocytosis occurs in response to ATPase inhibitors (Matt et al. 1980), the pump function appears possible, although we have no definite proof for this assumption. Protein phosphorylation would also be compatible with our cytochemical findings (Plattner et al. 1977, 1980) but this interpretation would still require biochemical confirmation. A Ca 2+ channel function was inferred by Satir and Oberg (1978) but it was shown later, that an alternative interpretation of their results would be possible (Matt et al. 1980), although their concept could be correct. As to contractile elements, it was shown by immunofluorescence (rabbitanti (Paramecium) actin IgG) and affinity fluorescence (DNase I, heavy meromyosin) labeling (Tiggemann and Plattner 1981) as well as by immuno-electron microscopic methods (Tiggemann et al. 1981) that the potential fusion sites proper, i.e., the "connecting material" regions, are devoid of actin (Plattner et al. 1982; see Fig. 6). This questions any direct interference of actin (or microfilaments, respectively) in the membrane fusion process — in opposition to earlier assumptions along these lines (Poste and Allisson 1973). In conclusion we assume that our cytochemical findings could indicate most likely the local presence of a Ca 2+ -dependent ATP-splitting activity, possibly combined with a Ca 2 +-transport function (pump and channel?). "Rosettes" and "connecting material" occur always together and only in exocytosis-capable Paramecium strains. This could be seen as being relevant for the structural assembly of the "rosette" MIP (which would be held together by the apposed "connecting material") and probably as being also functionally relevant, e.g., as a combined enzymeactivator type system (see discussion in Plattner et al. 1980). As to the latter possibility it would be rewarding to test for the presence of calmodulin or related proteins within the structural component with http://rcin.org.pl
Fig. 3. Freeze fractured trichocyst attachment sites (cell membrane) of Paramecium tetraurelia cells, strain nd 9. (a, b): nd 9 grown at the permissive temperature of 18°C, a — representing the plasmatic fracture face (P-face), b — showing the exoplasmic fracture face (E-face). Note the occurrence of a "ring" and of a "rosette" of MIPs in one of the fracture faces (P-face). (a', b'): nd 9 cells grown at the non-permissive temperature of 27°C are devoid of a "rosette" on both fracture faces (a' — P-face, b' — E-face). 100 000X. From Beisson et al. (1976) with kind permission of the author http://rcin.org.pl
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POLISH ACADEMY OF SCIENCES NENCKI I
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PROGRESS IN PROTOZOOLOGY Proceeding
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INTRODUCTORY REMARKS This Part II o
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183 In his abstract Mignot (1981) s
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PHYLOGENETIC RELATIONSHIPS AMONG PR
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187 algae by phycologists (Bourelly
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195 The foregoing subdivisions of A
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209 vine et al. 1980), there is no
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213 evidence for the assumption of
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REFERENCES 215 Bardele C. F. 1977:
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Page 47 and 48: THE TAXONOMIC POSITION OF EVGLENIDA
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Page 51 and 52: 225 brate cycle in vitro. Further c
Page 53 and 54: 227 could support the development o
Page 55 and 56: 229 for the development of methods
Page 57 and 58: IN VITRO CULTIVATION OF PARASITIC P
Page 59 and 60: Malaria IN VITRO CULTIVATION OF PAR
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Page 63 and 64: 237 Rai Choudhuri A. N.. Chowdhuri
Page 67 and 68: 241 Only those with 9-type 1 fronto
Page 71 and 72: THE MOLECULAR DIVERSITY OF TETRAHYM
Page 73 and 74: 247 in eukaryotes. It is about the
Page 75 and 76: Table 2 Mating species of Tetrahyme
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Page 85 and 86: 259 pattern; they do confirm our ju
Page 89 and 90: Table 13 Two-dimensional electropho
Page 91 and 92: 265 Cuny M., Milet M. and Hayes D.
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Page 105 and 106: MEMBRANE FUSIONS IN PROTOZOA 275 ba
Page 107 and 108: 277 B i 1 i n s k i M., Plattner H.
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Page 111 and 112: 281 structure and cytochemistry of
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Page 123 and 124: 293 Co-Chairman: Jan Kućera, Czech
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CONTENTS Introductory Remarks 179 B
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