Evidence of actin in the cytoskeleton of microsporidia.

Using transmission electron microscopy, immuno-electron microscopy, and biochemical techniques such as 2-D electrophoresis and immunoblotting, actin was found in all biological stages of the microsporidia Encephalitozoon hellem and Encephalitozoon cuniculi.

Mechanisms of microsporidial cell division: ultrastructural study on Encephalitozoon hellem.

The mitotic process in microsporidian Encephalitozoon hellem, a known human pathogen, has been studied with the aim of elucidating some ultrastructural aspects of its nuclear division. The presence of a nuclear spindle, of "electrondense spindle plaques" associated with the nuclear envelope and of cytoplasmic double walled vesicles are reported. We suggest that these "electrondense spindle plaques" serve as foci for intranuclear and cytoplasmic microtubule arrangements, similar to the microtubule organizing centers within the centrosomes of animal cells. The extent to which the microsporidial division process is comparable with that of more familiar eukaryotes such as yeast cells is discussed.

Sperm morphology of salamandrids (Amphibia, Urodela): implications for phylogeny and fertilization biology.

Mature spermatozoa belonging to four salamander species, Salamandrina terdigitata, Triturus alpestris, Triturus carnifex and Triturus vulgaris, have been investigated by electron microscopy. The sperm ultrastructure of these species was compared with that of previously examined urodeles (36 species and 20 genera) and with that of anurans and caecilians. Many phylogenetic considerations may be inferred as a consequence of comparative spermatology. Urodela appears to be a monophyletic order characterized by three sperm synapomorphies: the acrosomal barb, nuclear ridge and marginal filament. Cryptobranchoidea are confirmed to form a monophyletic suborder having two synapomorphic characters: absence of mitochondria in the tail, and cylindrical shape of the tail axial rod. Within the family Salamandridae, sperm morphology confirms the phylogenetic distance between Salamandrina and Triturus, as already pointed out on the basis of molecular and morphological characters. The very complex ultrastructure of spermatozoa confirms a previous opinion that internal fertilization is the ancestral condition of the Amphibia.

Spermatozoa of two Eledone species (Cephalopoda, Octopoda).

Spermatozoa from testes and spermatophores of two octopod species, Eledone cirrhosa and E. moschata, have been investigated by electron microscopy. At the base of the mature sperm acrosome of both species a well developed, periodic, conical structure is present. This structure is strikingly similar to that present in the Octopus sp. acrosome. Also the modalities of formation of such a structure during spermiogenesis show strong similarities between the Octopus and Eledone genera. The resistance to disruption of sperm chromatin of E. cirrhosa and E. moschata after treatments with SDS and mercaptoethanol which are known to dissolve disulfide-bridges, reveals the presence of S-S crosslinks.

Microsporidian spore wall: ultrastructural findings on Encephalitozoon hellem exospore.

A study of the spore wall of Encephalitozoon hellem was performed on thin sections, freeze-fracture, and deep-etched samples to obtain information on spore wall organization and composition. Our observations demonstrate that the spore wall is formed by an inner 30-35 nm electron-lucent endospore and an outer 25-30 nm electron-dense exospore. The exospore is a complex of three layers: an outer spiny layer, an electron-lucent intermediate lamina and an inner fibrous layer. Freeze-fracture and deep-etching techniques reveal that the intermediate lamina and the inner fibrous layer result from the different spatial disposition of the same 4-nm thick fibrils. In thin sections the endospore reveals a scattered electron-dense material that appears in the form of trabecular structures when analyzed in deep-etched samples. The presence of chitin in the exospore is discussed.

Action of gossypol on rat germinal cells. II. The acrosome.

The action of gossypol on the acrosomal complex in rats has been investigated by microscopical and submicroscopical methods. The drug displays its morphological action only on spermatozoa during the transit through the epididymis, causing malformations and vesiculations. It appears to exert a primary action on the S-S groups formation, disturbing morphological molding occurring in this period and inhibiting capacitation.

Sperm morphogenesis, structure and function in humans over 70 years old.

Semen and testicular biopsy samples from different aged human donors have been examined for any age related changes in sperm morphogenesis, structure and function. Various abnormalities and defects, some being unique to spermatozoon of elderly men, were observed at the light and electron microscope levels. In spite of this, the best fractions of ejaculated spermatozoa population maintains his function, as demonstrated by some complete egg penetrations observed with the 'zona free' hamster egg test system.

Morphogenesis of 'decapitated' spermatozoa in a man.

Study of biopsy specimens of a man with 'decapitated' spermatozoa indicated that the malformation was due to an overproduction of a membraneous vesicles system by the Golgi complex in the region between the centrioles and acrosome during the spermatid stage. The tails were almost normal in structure and 50% were motile in the ejaculate although few followed a straight trajectory.

Further observations on the morphogenesis of the round headed human spermatozoa.

Sperm and testicular biopsies of an infertile human patient have been investigated using histochemical and electron microscopical technique. Spermiogram revealed a head defect, characterized with lacking acrosome and round and immature nucleoplasm, occuring in practically all cells and coiled tails in about a half of spermatozoa. EM study of spermatids has shown an abortive development of acrosome, whose primordium failed to attach the nucleus and expand, instead regressed. The nucleus failed in shaping and retarded in maturing, a disturbance apparently associated with the aplasia of hypoplasia of caudal manchette. The role of zinc in nuclear differentiation and the shape of head in the movement pattern are discussed.