The risk of using monoclonal or polyclonal commercial antibodies: controversial results on porcine sperm CD44 receptor identification

Presence of the hyaluronan (hyaluronic acid, HA) receptor CD44 on spermatozoa has been difficult to pursue, mostly obeying to the use of different commercial mono‐ and/or polyclonal antibodies, often lacking proper controls. Here, we describe how the presence (Western blotting) and specific location (immunocytochemistry) of the CD44 receptor differs in ejaculated pig spermatozoa depending on the type of antibody and protocol used. While we were able to detect binding to spermatozoa and mark its presence in the sperm membrane, the use of blocking peptides clearly indicated that only the monoclonal antibody could confirm the specific presence and location of the CD44 receptor, whereas the polyclonal antibody was detecting multiple presumed CD44 isoforms or degraded proteins thus proving unspecific. These results call for strict protocols when attempting immunological determination of sperm membrane receptors.     

Detection of Glycosylated Proteins in Rabbit Oviductal Isthmus and Uterine Endometrium During Early Embryo Development

In this study, lectin histochemistry was performed on paraffin sections to compare carbohydrate expression of oviductal isthmus and uterine endometrium in rabbits during early embryo development. Rabbit embryos are surrounded not only by the zona pellucida but also by tubal secretion‐derived mucinous coat material, the mucin coat. Twenty sexually mature females were euthanized at 0 (pre‐ovulatory group) and 24, 72 and 96 h after insemination (pseudopregnancy group). The following lectin‐binding agents were used: Arachis hypogaea, Peanut (PNA) to label galactosyl (β‐1,3)N‐ acetyl‐galactosamine, Dolichos biflorus Agglutinin (DBA) to label galactosyl (β‐1,4)N‐ acetyl‐galactosamine, Lens curinaris (LCA) to label α‐‐mannose, α‐d ‐glucose and Pisum sativum agglutinin (PSA) to label α‐d ‐mannose, α‐d ‐glucose. Blood was collected by cardiac puncture, and direct enzyme immunoassay technique was used to measure progesterone concentration. A significant increase in total plasma progesterone concentrations was detected at 96 h post‐ovulation when compared with 0, 24 and 72 h post‐ovulation (2.9 ± 0.5 vs 0.5 ± 0.15, 1.6 ± 0.5 and 1.5 ± 0.4 ng/ml, at 96 h vs 0, 24 and 72 h post‐ovulation, respectively). No differences between pre‐ovulatory and pseudopregnant females were observed for glycoprotein localization in isthmus. In contrast, in the endometrium, differences in the glycoprotein detection between pre‐ovulatory and pseudopregnant stages were detected. PNA to label galactosyl (β‐1,3)N‐ acetyl‐galactosamine was not detected at the pre‐ovulatory stage, but its presence was detected at 24 h after ovulation. Both PSA and LCA to label α‐d ‐mannose, α‐d ‐glucose were only detected at 72 h after ovulation. DBA detection was similar for all stages of the reproductive cycle. Therefore, N‐acetyl‐galactosamine secreted from isthmus could be involved in the formation of the embryonic mucin coat. d ‐galactose (PNA), d ‐glucose and d ‐mannose (PSA and LCA) might be crucial for the implantation period.     

Discovery of a low-mass brown dwarf companion of the young nearby star G 196-3

A substellar-mass object in orbit at about 300 astronomical units from the young low-mass star G 196-3 was detected by direct imaging. Optical and infrared photometry and low- and intermediate-resolution spectroscopy of the faint companion, hereafter referred to as G 196-3B, confirm its cool atmosphere and allow its mass to be estimated at 25-10+15 Jupiter masses. The separation between the objects and their mass ratio suggest the fragmentation of a collapsing cloud as the most likely origin for G 196-3B, but alternatively it could have originated from a protoplanetary disc that has been dissipated. Whatever the formation process was, the young age of the primary star (about 100 million years) demonstrates that substellar companions can form on short time scales.