Electron microscope studies of human spermatozoa.

Semen of 40 healthy fertile men aged between 22--44 years was investigated. A triple morphological investigation of the semen was performed in each person. For the ultramicroscopic evaluation the semen specimens were selected according to the quantative criterion of normospermic. The ultrastructure of spermatozoon was described in comphiance with its division into head, neck and tail. The substructure of the axial fibre was separately analyzed. The physiological role of individual organelles of normal spermatozoon in fertilization was discussed.     

Electron microscope studies of glycogen synthase

Summary Glycogen synthase from rabbit muscle was examined with the electron microscope. In preparations of the completely converted glucose-6-phosphate dependent form (GSD) and the independent form (GSI) three structures were observed: toroids, hexagons and stacks of four elements which appear to be aggregates of four toroids. Toroids can be formed from hexagons by radial inward movement of subunits which form the vertices of the hexagons. Analysis of the dimensions of these structures and comparison of the known chemistry of the enzyme to the subunits as inferred from electron microscopy suggests a model for the structure of glycogen synthase. The model allows predictions of types of subunits in the enzyme, their relation to phosphorylatable and -SH sites and the possibilities of control by small effector molecules.     

Electron microscope studies of reconstituted eucollagen

The reconstitution of solutions of calf-skin eucollagen, obtained by solubilizing the collagen by pretreatment with cold alkali, has been studied in the electron microscope.As with tropocollagen, regular structures such as long-spacing segments, long-spacing fibrils, banded fibrils (220 Å spacing) and banded fibrils (650 Å spacing) were obtained, together with fibrils showing no periodic banding.From the close dimensional similarities between the structures derived from these two proteins, it apears that a substantial proportion of eucollagen molecules which can be isolated from mature collagen fibrils (which in the native state are mostly insoluble in citrate buffer) are similar in form and dimensions to those of tropocollagen.The slight differences in the reconstitution behaviour between the two proteins are interpreted in terms of their differing charge distribution.The results confirm that the alkaline pretreatment used in the preparation of eucollagen is successful in producing soluble material of regular physicochemical properties. They also support the view that the 650-Å band spacing of the mature native collagen fibril does indeed arise from the overlapping, by three quarters of their length, of tropocollagen-like molecules.     

Electron microscope studies of fish lymphocytes and thrombocytes

No observable differences were noted in electron microscopic studies between brown trout, Salmo trutta L., and carp, Cyprinus carpio L., lymphocytes and thrombocytes separated by the Ficoll-Paque technique. Transmission electron microscopy showed a similar ultra-structure of fish lymphocytes to those of other reported species. Scanning electron microscopy showed that these lymphocytes studied all had a villus structure and the thrombocytes clearly showed their spindle-shaped structure.     

Electron microscope studies of Fasciola hepatica. X. Egg formation

Evidence obtained would suggest that the processes involved in egg formation in Fasciola hepatica occur in the following sequence. The egg constituents, namely an ovum and some vitelline cells, pass through the proximal ootype and as they do so they are smeared by the secretions of Mehlis' gland which have accumulated there. A temporary interface is set up between the Mehlis' gland secretion and the fluid which surrounds the egg constituents. Shell globules are released by the vitelline cells and coalesce on the inner aspect of the interface. At the same time some of the Mehlis' secretion diffuses across the interface, thereby bringing about the dissociation of the interface. It is suggested that Mehlis' gland secretion brings about the fusion of the shell layer. During the initial stages of the process the developing egg is supported by the cells of the ootype epithelium. Later the egg passes into a wider, more distal part of the ootype where the process of shell deposition is continued. When complete, or almost complete, the egg passes into the uterus where changes indiciating the initial process of tanning are seen to take place. A thin, very uniform layer of Mehlis' gland secretion can still be identified on the surface of mature eggs.     

Electron microscope studies of thick filaments from vertebrate skeletal muscle.

Separated thick filaments have been prepared for electron microscopy by a method involving freeze-drying and shadowing. In the resulting filaments the individual heads of myosin molecules can be seen surrounding the filament shaft, which appears relatively smooth. Pairs of heads can frequently be seen to be emanating from a common origin. Myosin heads are found at distances up to 500 Å from the edge of the shaft.     

Electron microscope studies on the morphogenesis of plastids

Comparisons of the ultrastructure of plastids in three kinds of variegated leaves of tomato plants were made. No difference in the structure and development of chloroplasts in normal green leaves and in the green tissue of variegated leaves was found. The albescent tissues of chromosomal genetic variegated leaves contained only aberrant plastids, which were amoeboid or cup-shaped and had large vacuoles in the stroma. Ribosomes were absent from all plastids in this kind of variegated leaves. Three types of plastids, i.e. chloroplasts containing grana, chloroplasts lacking grana, and plastids lacking internal membranes, were present in the pale green tissues of the variegated leaves of extrachromosomal genetic tomato mutants. Depending on the distribution of these plastids, five cell types were observed in these tissues. Ribosomes were present in all plastids in this type of variegated leaves. In the albescent tissues of variegated leaves induced by streptomycin treatment, two kinds of plastids were observed, one containing giant grana and the other lacking organized internal membranes. A common feature of plastids in this albescent tissue was the presence of light stainable ribosomes. It was suggested that the development of variegated leaves may be caused by blocking an early stage of plastid development. This work was carried out in the Department of Botany, University of California, Davis, by Grant-GB-11906 from National Science Foundation of U.S.A.