Cell junctions in the germinal epithelium may play an important role in spermatogenesis of the catfish P. fasciatum (Pisces, Siluriformes).

We identified adhesive junctions and gap junctions between Sertoli cells, between Sertoli and germ cells and between germ cells in the testis of P. fasciatum, a catfish of commercial relevance. To investigate the role of these junctions in spermatogenesis, as well as the molecular composition of the junctions, we performed an immunohistochemistry light microscopy as well as an immunogold labelling electron microscopy study with antibodies to adhesive and gap junctions proteins. Testes that were at different stages of spermatogenesis were used. Based on our morphological studies we speculate that Sertoli-germ and germ-germ cell adhesive junctions are important for maintaining the three-dimensional structure of the germinal cysts and an organized arrangement of the germ cells inside the cysts. Connexin 32 was identified in the germ cells and in the cysts walls. Our observations also suggest that Sertoli-germ and germ-germ cells gap junctions may be involved in the mechanism of synchronous development of germ cells.

Cloning and expression of calglandulin, a new EF-hand protein from the venom glands of Bothrops insularis snake in E. coli.

The EF-hand protein family is comprised of many proteins with conserved Ca(2+)-binding motifs with important biological roles in intracellular communication. During the generation of Expressed Sequence Tags (ESTs) from the venom glands of the Viperidae snake Bothrops insularis, we identified a cDNA coding for a putative Ca(2+) binding protein with four EF-hand motifs, named here calglandulin. The deduced amino acid sequence displayed the greatest sequence similarity with calmodulin (59%), followed by troponin-C (52%). The encoded polypeptide was first expressed in Escherichia coli as a 6XHis-tagged fusion protein. The expressed protein was purified by Ni(2+)-charged affinity chromatography and circular dichroism (CD) spectroscopy confirmed the prevalence of alpha-helix as observed in calmodulin/calmodulin-like proteins. A polyclonal antiserum was generated in mice using this recombinant calglandulin. To investigate the tissue-specific biological occurrence of this protein, this antiserum was used in Western blot experiments, which revealed an immunoreactive band in samples of venom gland extracts from different snakes, but not in the crude venom or in brain, heart and other tissues. This exclusive occurrence suggests a specialized function of calglandulin in snake venom glands.