Changes in distribution of basic nuclear proteins and chromatin organization during spermiogenesis in the greater bandicoot rat, Bandicota indica

The original publication can be found at www.springerlink.comMale germ cells of the greater bandicoot rat, Bandicota indica, have recently been categorized into 12 spermiogenic steps based upon the morphological appearance of the acrosome and nucleus and the cell shape. In the present study, we have found that, in the Golgi and cap phases, round spermatid nuclei contain 10-nm to 30-nm chromatin fibers, and that the acrosomal granule forms a huge cap over the anterior pole of nucleus. In the acrosomal phase, many chromatin fibers are ∼50 nm thick; these then thickened to 70-nm fibers and eventually became 90-nm chromatin cords that are tightly packed together into highly condensed chromatin, except where nuclear vacuoles occur. Immunocytochemistry and immunogold localization with anti-histones, anti-transition protein2, and anti-protamine antibodies suggest that histones remain throughout spermiogenesis, that transition proteins are present from step 7 spermatids and remain until the end of spermiogenesis, and that protamines appear at step 8. Spermatozoa from the cauda epididymidis have been analyzed by acid urea Triton X-100 polyacrylamide gel electrophoresis for basic nuclear proteins. The histones, H2A, H3, H2B, and H4, transitional protein2, and protamine are all present in sperm extracts. These findings suggest that, in these sperm of unusual morphology, both transition proteins and some histones are retained, a finding possibly related to the unusual nuclear form of sperm in this species.Pakawadee Worawittayawong, Chris Leigh, Wattana Weerachatyanukul, Sirikul Manochantr, Prasert Sobhon, William G. Breed and Prapee Sretarugs

Molecular characterization and analysis of a truncated serotonin receptor gene expressed in neural and reproductive tissues of abalone

In molluscs, the neurotransmitter serotonin (5-HT) has been linked to a variety of biological roles including gamete maturation and spawning. The possible involvement of 5-HT in abalone gamete release was demonstrated by a dose-dependent increase in Haliotis rubra gonad contractile bioactivity following 5-HT stimulation. Physiological functions associated with 5-HT, are mediated through binding to 5-HT receptors. A cDNA encoding a putative 5-HT receptor consisting of 359 amino acids was isolated from the tropical abalone H. asinina, termed 5-HT1 ha. The 5-HT1 ha shares G-protein-coupled receptor motifs with metazoan 5-HT receptors, including predicted transmembrane domains, active sites for protein kinase action, and N-linked glycosylation sites. However, the third intracellular loop of 5-HT1 ha is relatively short, and only six transmembrane domains are predicted, implying a truncated receptor. Phylogenetic analysis with known 5-HT receptor genes suggests that 5-HT1 ha belongs to the type 1 5-HT receptor family. Expression analysis by RT-PCR showed that 5-HT1 ha&nbsp; mRNA was present in all tissues examined, including the neural ganglia and gonad tissues. Immunocytochemistry revealed the presence of 5-HT1 ha specifically within the soma of neuronal cells located in the outer cortex of both cerebral and pleuropedal ganglia. In ovarian and testicular tissues, 5-HT1 ha immunoreactivity was observed in epithelial cells of the outer capsule and connective tissue of the trabeculae to which the gamete follicles adhere. Whether this receptor transcript is translated to a functional protein needs to be verified, but if so, it could play a role in reproduction.<br /