Fig. 1. Localization of mAb H22 antigen in the outer wall of nematocysts. (A) Isolated nematocysts of Hydra. The different capsule types are: d, desmoneme; i, holotrichous isorhiza; s, stenotele. One of the stenoteles has discharged (s^*). (A') Immunofluorescence of mAb H22 viewed by confocal microscopy (maximum projection) in the isolated nematocysts shown in A. (B) Mature, isolated nematocyte of Hydra. Note the size of the nematocyst vesicle, which fills almost the whole cell (N, nucleus). (C) EM immunogold labeling of mAb H22 in the wall of a Hydra nematocyst. Gold particles are exclusively found in the outer wall (ow) and not in the inner wall (iw). (D) SDS-PAGE and western analysis of whole Hydra and isolated capsules. The protein of 500,000 isolated capsules was compared with 1/5 Hydra (1/5H) by silver-staining. In a western blot, protein of 1 Hydra (1H) and 500,000 capsules separated by SDS-PAGE were probed with mAb H22 and minicollagen antibody. A high molecular weight protein is detected by mAb H22 in isolated capsules, but not in whole Hydra. Minicollagens detected by minicollagen-1 antibody represent the major proteins of the capsule. Bars, 5 µm (A,B); 100 nm (C).

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