Thornhill, Alan R.

The mammalian cell nucleus consists of numerous compartments involved in the regular unfolding of processes such as DNA replication and transcription, RNA maturation, protein synthesis and cell division. Knowledge is increasing of the relationships between high-order levels of chromatin organization and its spatial organization, and of how these relationships contribute to the various functions carried out in the nucleus. We have studied the spatial arrangement of mouse telocentric chromosomes 5, 11, 13, 15, 16 and 17, some of their metacentric Robertsonian derivatives, and X and Y chromosomes by whole chromosome painting in male germ (spermatogonia, pachytene spermatocytes and spermatids) and Sertoli cells of homozygous and heterozygous individuals. Using dual-colour fluorescence in situ hybridization we found that these chromosomes occupy specific nuclear territories in each cell type analysed. When chromosomes are present as Robertsonian metacentrics in the heterozygous state, that is, as Robertsonian metacentrics and their homologous telocentrics, differences in their nuclear positions are detectable: heterozygosity regularly produces a change in the nuclear position of one of the two homologous telocentrics in all the cell types studied. In the Robertsonian heterozygotes, the vast majority of the Sertoli cells show the sex chromosomes in a condensed state, whereas they appear decondensed in the Robertsonian homozygotes. As the Robertsonian heterozygosities we studied produce a chromosomally derived impairment of male germ-cell differentiation, we discuss the possibility that changes in chromosome spatial territories may alter some nuclear machinery (e.g., synapsis, differential gene expression) important for the correct unfolding of the meiotic process and for the proper functioning of Sertoli cells.

The objectives of this study were to determine the effectiveness of a novel, trypsinized density gradient treatment designed to remove viruses from semen and to evaluate sperm viability after treatment. Exp. 1: Cryopreserved human semen (n = 6 donors) was layered on 2-mL columns of 45% Isolate (Irvine Scientific, Santa Ana, CA, USA) with or without 0.25% trypsin (trypsin-exposed and control, respectively), which overlaid 2-mL columns of 90% Isolate with or without 10 µg/mL soy-based trypsin inactivator (Sigma, St. Louis, MO, USA) and centrifuged (700g for 30 min). The layering of multiple density gradients is facilitated by a novel polypropylene tube insert, which also prevents contamination when extracting treated sperm (USA and international patents pending). Pellets were washed and then incubated at room temperature. Sperm were examined (motility and supravital staining) at 0, 2, 24, and 48 h post-treatment and the results evaluated using Wilcoxon Signed Rank and Rank Sum tests. Exp. 2: A cytopathic cell (MT-2) assay was conducted (6 replicates) to determine the effect of trypsin (1-min exposure) on HIV-1 RNA infectivity. Viral replication was assessed by syncytium formation and p24 antigen production. Exp. 3: Two pools of fresh human semen (N1 = 3 and N2 = 8 donors) were inoculated (1:1) with 1 × 108 copies/mL of cultured HIV-1 RNA, and one pool (N2) was inoculated (1:1) with plasma collected from patients infected with either Hepatitis B DNA (HBV) or C (HCV) RNA viruses; spiked and non-spiked aliquots were processed as in Exp. 1. Treated sperm pellets were analyzed for HIV-1 or HBV and HCV concentrations by the Bayer Versant branched DNA (bDNA; version 3.0) and/or the Roche Amplicor quantitative RT-PCR (1.5 ultrasensitive) assays at Toga Laboratories (Pty), Ltd. (Edenvale, South Africa). As a result of Exp. 1, there was significantly (P < 0.05) lower motility (but not supravital staining) between trypsin-treated and control sperm at 0 h (58.0 vs. 69.3%) and 2 h (54.7 vs. 62.9%) post-washing; however, no differences were noted after 24 h (P > 0.05). In Exp. 2, trypsin exposure affected HIV-1 RNA infectivity negatively as compared to controls in terms of MT-2 cell syncytium formation and p24 antigen production. Results of the bDNA and/or RT-PCR assays in Exp. 3 indicated that the procedure effectively reduced HIV-1, HBV, and HCV viral copies in the spiked semen samples to undetectable levels or levels below clinical relevance. In conclusion, the novel trypsin density gradient procedure was effective for removing HIV-1, HBV and HCV from spiked semen without markedly affecting sperm survival. Extrapolation of these results to natural infections may be unfounded for viruses (e.g. HBV) that are thought to integrate into sperm chromatin.