Archive for the ‘Cell’ Category

Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(9)

Sperm interactions with heparin-like GAG may facilitate capacitation in vivo by inducing loss or modification of sperm surface molecules involved in sperm-oviduct binding. We in fact showed that GAG from fluids derived from dominant follicles were very efficient in competing for carbohydrate binding to the sperm surface (valid for all biotinylated carbohydrates tested). A chemically […]

Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(8)

More importantly, heparin itself competes with lectins for binding to the sperm surface. Moreover, bicarbonate and heparin-induced capacitation reduced carbohydrate-binding properties of the bovine sperm surface (this study). Indeed, capacitated sperm had a lower binding rate for fucose-BSA-biotin, using a flow cytometric assay) than did uncapacitated sperm. We were able to repeat this result not […]

Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(7)

This may explain why heparin interferes with bovine sperm-oviduct binding. An issue for further research is to decipher whether the sperm release is caused i) directly by extracellular GAG or ii) indirectly via sperm capacitation that induces sperm surface changes and subsequently causes the release, or iii) a combination of both processes.

Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(6)

Although heparin had no effect on the binding of the uncapacitated sperm to the oviductal epithelium, it was recently shown that heparin acts as a strong inhibitor of sperm binding and also a quick releaser of sperm bound to the oviduct epithelium (this study, ). Heparin (and fucoidan) induce an increase in flagellar-beat frequency and […]

Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(5)

The most potent inhibitor for sperm-oviduct binding was fucoidan, and indeed, polysaccharides like mannan and fucoidan were also highly effective in preventing fucose-PAA-biotin binding to immobilized SPM. In fact, mannan-BSA-biotin and fucoidan-biotin had higher affinity for immobilized SPM than fucose-PAA-bi-otin. We should consider here that the conjugates used differ in stoichiometry of carbohydrate and biotin […]

Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(4)

The difference may arise from experimental differences as, in our approach, isolated and immobilized SPM were used as binding templates for fucose- or LeA-PAA-biotin (each polyacryl-amide-biotin conjugate contains approximately 20 mol% of fucose or LeA). In contrast, Suarez et al. used a bioassay in which unconjugated (free-form) fucose and LeA was used to block live […]

Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(3)

Sperm-oviduct interactions cannot be investigated in situ at the biochemical level. However, several in vitro studies have shown that mammalian sperm binding to the oviduct is mediated by carbohydrate interactions. For bovine species, the animal model of the current investigation, this interaction appears to be fucose specific. We have set up a biochemical assay to […]

Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(2)

This process may even lead to cell deterioration that was not observed, in fact only live sperm cells were imaged. Moreover, paraformaldehyde-fixed cells showed similar distribution of biotinylated carbohydrate probes (results not shown), which would at least indicate against a lateral movement of the sperm lectins from a distinct surface area of the sperm head […]

Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(1)

In this study, we have developed a new assay to biochemically quantify carbohydrate affinity of the apical head plasma membrane of bovine sperm. The SPM was purified and immobilized and biotinylated carbohydrate probes were used for quantitative detection of binding as well as binding competition. The effects of in vitro capacitation factors such as bicarbonate […]

Dynamics of Carbohydrate Affinities at the Cell Surface: RESULTS(10)

In the ampulla, they were also found within apical protrusions of the secretory cells, indicating their secretory origin (Fig. 9). The secretory activity of the ampulla is maximal around ovulation and probably increases the amount of GAG in the isthmus, where it may facilitate sperm release. A concentration of 403.5 |xg/ml of sulfated GAG was […]

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