[Ultrastructure of boar sperm membranes prepared by freeze-fracturing].
The objective of the present paper was to describe the topographic orientation of intramembraneous particles (IMP) in the membranes of freshly ejaculated boar spermatozoa applying the method of freeze fracturing. Disc clusters of IMP's could be distinguished in the acrosome-covering plasma membrane (PF). The border of the head to a distance of about 0.3 micron seemed to contain no IMP's (Figs. 1, 2). In the postacrosomal region in an anterior direction from the posterior ring the IMP's were found to be arranged in palissade slant rows. Statistical measurements of 20 spermatozoa (Tab. I) indicated that the slant rows extended to the greatest distance in the lateral part of the head, up to 0.67 micron (+/- 1.45-0.39) from the posterior ring. In the middle of the head the rows extended to a distance of 0.18 micron (+/- 0.10-0.42). The transition spot between the zone of sparse IMP's and the zone of densely arranged IMP's was at a distance of 1.63 microns (+/- 1.87-0.69) in an anterior direction from the posterior ring (Figs. 3, 4). In the flagellum in the plasma membrane (PF) the first spot of an ample occurrence of IMP's is located in the first mitochondrion in the spiral. The IMP clusters follow the cicumferential orientation of mitochondria in the mitochondrial spiral. The IMP's were missing in the spaces between the spiral coils (Fig. 5). The membranes of the mitochondria contain a large amount of IMP's. This activity is transferred to the clinging part of the plasma membrane (Fig. 6). A larger accumulation of IMP's can be seen at the spot where the plasma membrane covers the annulus (Fig. 7). In the plasma membrane of the main segment of the flagellum the IMP's are distributed irregularly in PF, and also in EF (Fig. 8). The EF surfaces of the plasma membrane had in general an indistinct structural organisation of IMP's. The distribution of IMP's in acrosomal membranes was found to be irregular. The postacrosomal lamina in the freeze fracturing did not look like a morphologically identifiable structure. In the nuclear envelope delimiting the posterior nuclear space, nuclear pores could be identified (Fig. 9). No nuclear pores could be seen in the nuclear envelope clinging to the posterior part of the nucleus. At this spot smaller IMP's were observed which could be a part of the proteins of the filaments connecting the concave surface of the head with the convex articular surface of the flagellum. These filaments connect the head and the flagellum (Fig. 10).(ABSTRACT TRUNCATED AT 400 WORDS)