Abstract. An hypothesis considering mitochondria as intracellular power-transmitting protonic cables was tested in human fibroblasts where mitochondria are thin and long and in rat cardiomyocytes where they show cluster organization. Mitochondria in the cell were specifically stained with fluorescent-penetrating cation ethylrhodamine, which electrophoretically accumulates in the mitochondrial matrix.A 40-1xm-long mitochondrial filament of fibroblast was illuminated by a very narrow (~0.5 ~tm) laser beam to induce local damage of the mitochondrial membranes. Such a treatment was found to induce quenching of the ethylrhodamine fluorescence in the entire filament. According to the electron microscope examination, the laser-treated filament retained its continuity after the laser illumination. Other mitochondrial filaments (some of which were localized at a distance <10 ~tm from the laser-treated one) remained fluorescent. In a cell where mitochondrial filaments seemed to be united in a network, laser illumination of one filament resulted in fluorescence quenching in the whole network, whereas fluorescence of small mitochondria not connected with the network was unaffected.The illumination of cardiomyocyte was found to result in the fluorescence quenching not only in a laserilluminated mitochondrion but also in a large cluster of organeUes composed of many mitochondria. Electron microscopy showed that all the mitochondria in the cluster change from the orthodox to the condensed state. It was also found that mitochondria in the cluster are connected to one another with specific junctions. If a mitochondrion did not form junctions with a quenched cluster, its fluorescence was not decreased even when this mitochondrion was localized close to an illuminated one. The size of the mitochondrial cluster may be as long as 50 lam. The cluster is formed by branched chains of contacting mitochondria, which may be defined as Streptio mitochondriale. In the cardiomyocyte there are several mitochondrial clusters or, alternatively, the quenched cluster is a result of decomposition of a supercluster uniting all the mitochondria of the cell. Cluster organization of mitochondria could also be revealed when a single mitochondrion was punctured in situ with a microcapillary. The obtained data are in agreement with the idea that mitochondrial junctions are H ÷ permeable so that, within the cluster, A~ may be transmitted from one mitochondrion to another.The above results are consistent with the assumption that mitochondrial filaments or networks represent a united electrical system. (Possible functions of extended mitochondrial systems are discussed.) M EMBRANE structures containing energy-releasing and energy-consuming enzymes are defined as coupling membranes. If within one membrane there are a AIiH-generating respiratory chain and an H ÷-ATP synthase, respiration and phosphorylation can be coupled via A~H (19). It is obvious that both A~ and ApH constituents of AIiH, once they are formed across it, immediately spread along the membran...

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Structural polarity of centriole has been shown by analyzing serial sections of centrioles in the tissue culture cells of mouse, man, pig and Chinese hamster. Its major component is nine microtubule triplets. The inclination of the triplets towards the radius at the proximal end of the centriole is smaller than at the distal one. The internal tubule of the triplet has a smaller diameter than the middle and external ones; The triplets are bound by links of various nature all over their length. In the middle part, in the centriole lumen there is an amorphous hub; in the distal part, a thin fibre that is helically wound. In the proximal part, there are bases along the triplets, and handles stretch from the internal tubules. In the middle and distal parts, there are accumulations of an electron dense substance along the middle tubules. At the distal end, the centriole lumen is filled with an amorphous substance, whereas the proximal end is free from it. From outside, appendages are attached to the triplets at the distal end. The centriole structure is identical in all the cell types studied, except for those of Chinese hamster.

Nucleolus-organizing regions (NORs) at some stages of the cell cycle (G0 period, G2 period and mitosis), differing in the level of NOR transcription activity, were studied on ultra-thin serial sections of pig embryo kidney cells. Particular attention was given to the spatial organization of fibrillar centers (FCs) in the nucleoli and to comparing the number of FCs with that of NORs. It was shown that within nucleoli, FCs may be located singly or form groups surrounded by a dense fibrillar component. The overall number of FCs exceeds that of NORs 1.7-fold in the G0 period, and 4.6-fold in the G2 period. At prophase, with progressive condensation of chromosomes and NOR inactivation, the number of FCs decreases and at metaphase corresponds to the number of silver-stained NORs. The data thus obtained make it possible to conclude that in active nucleoli, the number of FCs is higher than that of NORs. Proceeding from these numerical and ultrastructural data, it is suggested that a single NOR of pig embryo kidney cells corresponds to one "fibrillar complex", i.e., to an association of a different number of FCs with the dense fibrillar component. These "fibrillar complexes" contain 1 to 3 FCs in the G0 period and 1 to 12 FCs in the G2 period.