Biomedical subjects

N F Scully

Publications and source records attributed to N F Scully.

6 recordsLinked to original sources

PubMed1993

Cell surface beta 1,4 galactosyltransferase on primary spermatocytes facilitates their initial adhesion to Sertoli cells in vitro.

The Sertoli cell maintains the cytoarchitecture of the seminiferous epithelium and provides support for the developing germ cells through specialized adhesive junctions. Despite the importance of this adhesive interaction, our understanding of germ cell-Sertoli cell interactions is limited. Previous studies have shown that beta 1,4 galactosyltransferase (GalTase) is present on the surface of mature sperm, where it mediates sperm binding to the egg zona pellucida. Since GalTase is present on the surface of early spermatogenic cells long before it is required for sperm-egg recognition, we determined in this study whether GalTase on developing germ cells functions during adhesion to Sertoli cells. Consistent with such a function, GalTase was localized by indirect immunofluorescence to areas of putative germ cell-Sertoli cell contact. More directly, anti-GalTase IgG and Fab fragments inhibited the initial adhesion of spermatocytes to Sertoli cell monolayers; however, anti-GalTase antibodies were less able to inhibit spermatocyte-Sertoli cell adhesions after prolonged co-culture, presumably due to stabilization of the intercellular adhesion. After meiosis, surface GalTase begins to acquire its final distribution overlying the intact acrosome; there it was no longer able to facilitate germ cell adhesion to Sertoli cells. Indirect immunofluorescence and direct enzyme assays showed that Sertoli cells also expressed surface GalTase; however, most GalTase was confined to the basal cell surface where it was inaccessible to germ cells, but where it may function in adhesion to the underlying basal lamina. Preblocking studies confirmed that surface GalTase on the spermatocyte surface, rather than on the exposed apical Sertoli surface, mediated germ cell-Sertoli cell adhesion, presumably by binding to glycoside ligands on the Sertoli cell.

Animals↗

PubMed1993

Tests of sperm function for evaluation of the male: Penetrak and Tru-Trax.

OBJECTIVE: To evaluate the Penetrak (Serono Laboratories, Norwell, MA) and Tru-Trax (Humagen, Charlottesville, VA) bovine cervical mucus (CM) penetration assays and to correlate results to parameters of semen analysis and male factor diagnosis. DESIGN: Prospective, nonrandomized, controlled study. PARTICIPANTS: Two hundred thirty-six males undergoing evaluation for male factor infertility and 37 fertile semen donors. MAIN OUTCOME MEASURES: Human sperm penetration in bovine CM measured by the Penetrak and Tru-Trax assay systems correlated to sperm density, motility, forward progression, and clinical diagnosis. RESULTS: Two parameters of semen analysis, motility and density were correlated to the distance traversed by the vanguard sperm in both Penetrak and Tru-Trax assays. Penetrak results were significantly correlated to male factor infertility diagnosis. CONCLUSIONS: Both assays were reliable and highly reproducible, and the Tru-Trax assay was correlated to its predecessor, Penetrak. Although Penetrak and Tru-Trax were correlated to motility and density, no correlation coefficient was > 0.6, suggesting that these assays measure a facet of sperm function that is independent of semen analysis.

Animals↗

PubMed1990

Elevated galactosyltransferase activity on t-bearing sperm segregates with T/t-complex distorter loci-2.

Sperm bearing complete t-haplotypes are preferentially transmitted during fertilization from heterozygous +/t males, often in excess of 95% relative to their (+)-bearing meiotic partner. Sperm from t-bearing males have an approximate two- to fourfold increase in beta 1,4-galactosyltransferase (GalTase) activity, a cell surface protein that mediates sperm binding to the egg zona pellucida. The elevated GalTase activity strictly correlates with the preferential transmission of t-sperm from +/t males, since eight other enzymes show normal levels of activity on t-sperm. Furthermore, sperm bearing proximal partial t-haplotypes, which are no longer favoured during fertilization, have normal levels of GalTase activity. Nevertheless, it has been unclear whether the elevated sperm GalTase activity on t-sperm is due to specific loci in the distal segment of the T/t-complex, or rather, is an indirect consequence of the abnormal sperm function characteristic of +/t and tx/ty males. In this study, it is shown that the elevated sperm GalTase activity is due specifically to factors that reside within the distal segment of the T/t complex, which also contains Tcd-2, the strongest of the distorter loci. Since the structural locus for GalTase is located on mouse chromosome 4, these results also show that T/t-complex alleles on chromosome 17 are regulatory in nature and affect the expression of sperm surface components critical for normal fertilization. Models are presented to explain how elevated GalTase activity could contribute to sperm transmission distortion.

Animals↗

PubMed1988

Stage-specific increase in cell surface galactosyltransferase activity during spermatogenesis in mice bearing t alleles.

Mouse sperm surface galactosyltransferase (GalTase) mediates fertilization by binding to its appropriate glycoconjugate substrate in the egg zona pellucida. GalTase is present throughout all stages of spermatogenesis, during which time it redistributes within the plasma membrane from a uniform, diffuse distribution on primary spermatocytes to a restricted domain overlying the dorsal surface of the acrosome. Previously, we have shown that GalTase activity is elevated on transmission-distorting t-bearing sperm populations, relative to normal sperm, and in this paper, we define the stage when surface GalTase activity becomes elevated during t spermatogenesis. GalTase specific activity is equal between normal and t-bearing primary spermatocytes, but following meiosis, surface GalTase activity becomes elevated nearly fourfold on t-bearing round spermatids. The increased GalTase activity on t-bearing spermatids is not due to decreased hydrolysis of the GalTase substrates, and is appropriately localized over the acrosomal region, even on misshapen sperm heads occasionally seen in t-sperm populations. These studies define the stage when a specific biochemical defect associated with mutant alleles of the T/t complex first becomes detectable. The t factors that elevate GalTase activity on round spermatids may be similar to previously identified t-specific testicular proteins that are maximally expressed at the same developmental stage, and which map to the same portion of the T/t complex.

Alleles↗

PubMed1987

Spatial and temporal expression of cell surface galactosyltransferase during mouse spermatogenesis and epididymal maturation.

We have previously shown that sperm-egg recognition in the mouse is mediated by the binding of galactosyltransferase (GalTase) on the sperm surface to its appropriate glycoside substrate in the egg zona pellucida [L. C. Lopez, E. M. Bayna, D. Litoff, N. L. Shaper, J. H. Shaper, and B. D. Shur (1985) J. Cell Biol. 101, 1501-1510]. In the present study, we have defined the spatial and temporal expression of surface GalTase during spermatogenesis and epididymal maturation. Purified populations of spermatogenic cells were isolated by unit gravity sedimentation, and surface GalTase expression was determined by indirect immunofluorescence and by direct enzymatic assay. GalTase is present on the surface of all spermatogenic cells assayed. During differentiation, there is a progressive redistribution of GalTase from an initially diffuse and uniform localization on the surface of primary spermatocytes to a restricted plasma membrane domain overlying the dorsal aspect of the mature acrosome. This apparent redistribution of surface GalTase was confirmed by direct enzymatic assays, which show that surface GalTase activity, normalized per cell, remains relatively constant throughout spermatogenesis, despite a drastic reduction in cell surface area. When normalized to the relevant cell surface area, the GalTase concentration per square micrometer increases 77-fold from pachytene spermatocytes to cauda epididymal sperm. Cell surface GalTase is thought to be a cytoskeletally associated transmembrane protein [N. L. Shaper, P. L. Mann, and J. H. Shaper (1985) J. Cell Biochem. 28, 229-239]; consequently we examined whether cytoskeletal components may be involved in the redistribution of GalTase during spermatogenesis. beta-Tubulin, monomeric actin, and filamentous actin were found to be present during spermatogenesis, as assayed by indirect immunofluorescence and by Western immunoblotting. alpha-Actinin and vinculin were not detectable under these conditions and served as negative controls. During spermatogenesis, the distribution of tubulin coincides with the appearance of the mitotic spindle, flagellum, and manchette. On the other hand, the distribution of filamentous actin coincides with surface GalTase, suggesting that actin-containing microfilaments may participate in the redistribution of surface GalTase during spermatogenesis.

Animals↗

PubMedDate not supplied

Cell surface galactosyltransferase as a recognition molecule during development.

Recent results from our laboratory suggest that a variety of cellular interactions during development are mediated, in part, by the binding of a cell surface enzyme, galactosyltransferase (GalTase), to its specific lactosaminoglycan (LAG) substrate on adjacent cell surfaces and in the extracellular matrix. Our present interest in surface GalTase developed from earlier biochemical studies of a series of morphogenetic mutations in the mouse which map to the T/t-complex. These studies identified a specific defect in the regulation of surface GalTase activity on morphogenetically abnormal cells, while eight other enzymes showed normal activity. This led us to consider the unique function of surface GalTase in those cell interactions that are influenced by mutations of the T/t-complex. By using a multidisciplinary approach, which included genetic, biochemical and immunological probes, we have found that GalTase functions as a surface receptor during fertilization, early embryonic cell adhesions, and embryonic cell migration on basal lamina matrices. Recently, we have examined the expression of surface GalTase during spermatogenesis, as well as the fate of sperm GalTase following the acrosome reaction. This paper summarizes the results of these studies, as well as others, which suggest that GalTase functions as a surface receptor during those cell interactions regulated by the T/t-complex alleles.

Animals↗