PROGRESS IN PROTOZOOLOGY

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Fig. 6. Ultrathin section through a trichocyst attachment site of a Paramecium tetraurelia (K 401) cell after immunocytochemical staining for actin, using rabbit anti-(P aramecium) actin IgG coupled to horseradish peroxidase (type VII) for visualization by the diaminobenzidine technique. Only the microfilaments (mf) which surround the trichocyst tip are reactive; the trichocyst attachment site on the cell membrane (arrow) is negative. (The "inner lamellar sheath" within the trichocyst tip displays some endogenous electron density). 100 000 X. From Plattner et aL (1982) http://rcin.org.pl
273 the preliminary designation "connecting material". Such attempts have been started just recently. It deserves to be mentioned that the uppermost trichocyst tip (adjacent to the cell membrane) is always devoid of MIP; the "annulus" MIPs surround the fusion site proper somewhat below, so that this structure (like the "rings" within the cell membrane) seems to be situated outside the fusion zone proper. Exocytotic Systems in Other Protists and in Metazoa "Rosette" type MIP clusters (without a "ring") have been observed also over extrusomes of heliozoa (Davidson 1976) and sporozoa (Eivieria: Dubremetz and T o r p i e r 1978, Toxoplasma: Porchet and Tor pier 1977: Plasmodium: Dubremetz et al. 1979, Bannister, personal communication). In the case of sporozoa exocytotic events are believed to (participate in the host cell penetration (Eimeria: J e n s e n and Edgar 1976; Toxoplasma: Nichols and O'Connor 1981). During conjugation of the ciliate Euplotes the contents of ampullae are released by exocytosis and again "rosettes" were found at these sites (L u p o r i n i, personal communication). Nothing alike was reported for amoebae (for Entamoeba see Henley et al. 1976). There are so far no data available on the occurrence of "connecting material" in these cases. Among metazoa, exocytotic sites are characterized by conspicuous MIP aggregates only in motor endplates (c.f. Meldolesi et al. 1978). For many other systems it was claimed that MIPs would be removed from the fusion sites on a large scale before fusion (O r c i and Perrelet 1978). This view has recently been challenged for methodical reasons (Plattner 1981). Careful freeze-fracture experiments with various gland cells also showed that exocytotic fusion events in several mammalian gland cells might occur without any or with only a small MIP shift (Tanaka et al. 1980), so that MIPs might here also be located quite closely to the fusion zone. We arrive to the following conclusion. If some membrane (integrated and/or associated) proteins would stay close to the fusion site, they could exert a positive modulatory effect, e.g., by exerting a Ca 2 +-channel function as mentioned above or by changing the fusogenic properties of the tightly apposed membranes (to mention just two possibilities). Supporting evidence along these lines came recently from work with liposomes which fuse in the presence of physiological Ca 2 + concentrations only when supplemented with certain proteins (Z i m m e r b e r g et al. 1980), whereas previous work on lipo- 7 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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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
Page 61 and 62: IN VITRO CULTIVATION OF PARASITIC P
Page 63 and 64: 237 Rai Choudhuri A. N.. Chowdhuri
Page 65 and 66: PROGRESS IN PROTOZOOLOGY Proceeding
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
Page 83 and 84: Table 8 Percentage of DNA reanneali
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.
Page 95 and 96: MEMBRANE FUSIONS IN PROTOZOA 269 It
Page 97 and 98: Table 1 Characterization of exocyto
Page 99 and 100: Fig. 3. Freeze fractured trichocyst
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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.
Page 109 and 110: LIST OF SCIENTIFIC REPORTS presente
Page 111 and 112: 281 structure and cytochemistry of
Page 113 and 114: 283 LIST OF SCIENTIFIC REPORTS A. P
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Page 117 and 118: 287 LIST OF SCIENTIFIC REPORTS K. G
Page 119 and 120: LIST OF SCIENTIFIC REPORTS 289 R. A
Page 121 and 122: 291 LIST OF SCIENTIFIC REPORTS magn
Page 123 and 124: 293 Co-Chairman: Jan Kućera, Czech
Page 125 and 126: 295 LIST OF SCIENTIFIC REPORTS for
Page 129 and 130: INTERNATIONAL COLLABORATION AMONG P
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Page 149: CONTENTS Introductory Remarks 179 B
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