References of "Roberts, R. Michael"
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See detailMultiple pregnancy-associated glycoproteins are secreted by day 100 sheep placenta
Xie, Sancai; Green, Jonathan; Bao, Bagna et al

in Biology of Reproduction (1997), 57(6), 1384-1393

Pregnancy-associated glycoprotein (PAG)-1 (PAG1) and pregnancy-specific protein B are either identical or closely related antigens released by trophoblast binucleate cells of placentas of cattle. Sheep ... [more ▼]

Pregnancy-associated glycoprotein (PAG)-1 (PAG1) and pregnancy-specific protein B are either identical or closely related antigens released by trophoblast binucleate cells of placentas of cattle. Sheep and other ruminants produce similar products. There is evidence, however, that these antigens, which are related structurally to the pepsinogens and other aspartic proteinases, are not single gene products but members of an extensive family. Here, the sequential use of ammonium sulfate precipitation and Sepharose blue, anion-exchange, and cation-exchange chromatographies, as well as isoelectric elution from a Mono P column, has allowed several PAG1-related molecules to be purified from the medium after culture of explants from Day 100 sheep placentas. Each of these PAGs cross-reacted to a varying extent with a panel of three different anti-PAG1 antisera. Four of them, all of which were major secretory products of the placenta, were subjected to amino-terminal microsequencing. Although each was related to ovine (ov) PAG1, none was identical. Reverse transcription-polymerase chain reaction was then used to amplify PAG1-related cDNA from Day 100 placental RNA. Seven novel full-length cDNA, all distinct from ovPAG1, were identified from 25 cDNA selected for sequencing. Only two of these (ovPAG3 and ovPAG7) encoded polypeptides identical in sequence at their inferred amino termini to one of the PAGs (ovPAG65) purified from explant cultures. Even so, they were only 84% identical in overall sequence. The remaining five cDNA were unique. In situ hybridization analysis revealed that expression of ovPAG3 and ovPAG7, like that of ovPAG1, is confined to trophoblast binucleate cells. The data confirm that at Day 100 of pregnancy the ovine placenta produces many different PAGs, which differ considerably in sequence and immunological cross-reactivity. [less ▲]

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See detailA novel glycoprotein of the aspartic proteinase gene family expressed in bovine placental trophectoderm
Xie, Sancai; Low, Boon G.; Nagel, Robert J. et al

in Biology of Reproduction (1994), 51(6), 1145-1153

The pregnancy associated glycoproteins (PAG 1) that appear in the maternal serum of cattle and sheep soon after implantation are apparently inactive members of the aspartic proteinase family. Here we ... [more ▼]

The pregnancy associated glycoproteins (PAG 1) that appear in the maternal serum of cattle and sheep soon after implantation are apparently inactive members of the aspartic proteinase family. Here we describe the isolation of a highly abundant cDNA (PAG 2 cDNA) that represents a second member of this gene family which is structurally related to bovine PAG 1, ovine PAG 1, and pepsin (58%, 58%, and 51% amino acid sequence identity, respectively). The bovine PAG 2 cDNA was identified in two ways. First, the bovine placental library was screened under relatively nonstringent conditions with an ovine PAG 1 cDNA. The second fortuitous approach employed immunoscreening with an antiserum raised against a partially purified factor that competed with bovine LH for binding to the LH receptor on the CL of the ovary. The full-length cDNA (1258 bp) codes for a polypeptide of 376 amino acids. Bovine PAG 2, unlike bovine PAG 1, has a catalytic center with a consensus sequence of amino acids. Its mRNA is expressed in fetal placenta but not in other fetal organs, and is localized to both the mononucleate and binucleate cells of the trophectoderm, whereas PAG 1 is expressed only in binucleate cells. PAG 2 is synthesized by placental explants as a 70-kDa glycoprotein that is processed to several smaller molecules. Western blot analysis of culture media developed with epitope-selected antibodies to PAG 2 reveals several bands ranging in apparent M(r) from 31,000-70,000, which correspond in size to the polypeptides present in the preparation used for immunization [less ▲]

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See detailMolécules de la famille des protéases aspartiques dans le placenta des ruminants: hormones ou protéines ?
Beckers, Jean-François ULiege; Roberts, R. Michael; Zoli, André Pagnah et al

in Bulletin et Mémoires de l'Académie Royale de Médecine de Belgique (1994), 149(8-11), 355-367

The placenta of ruminant contains binucleate trophoblastic cells synthesizing proteins, migrating cross the barrier and fusing with endothelial cells of the endometrium. Recently described were two ... [more ▼]

The placenta of ruminant contains binucleate trophoblastic cells synthesizing proteins, migrating cross the barrier and fusing with endothelial cells of the endometrium. Recently described were two glycoproteins from the family of aspartic proteases, apparently lacking the enzymatic activity: the pregnancy associated glycorproteins I and II (PAGI and PAGII). The first (PAGI) is largely secreted in maternal blood, this characteristic copes with the lack of proteolytic activity. The second (PAGII) is not completely characterized. However, it binds to lutropin (LH) receptors with high affinity. This binding allows to assume that PAGII is likely the same as the bovine chorionic gonadotropin identified earlier (bCG). A better characterization of these glycoproteins (PAGI and PAGII) and other members of the family (PAGIII...) will answer these questions together with the unexplained invasive process of the placenta. [less ▲]

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See detailIdentification of the major pregnancy-specific antigens of cattle and sheep as inactive members of the aspartic proteinase family
Xie, Sancai; Low, Boon G.; Nagel, Robert J. et al

in Proceedings of the National Academy of Sciences of the United States of America (1991), 88(22), 10247-10251

Pregnancy in cattle and sheep can be diagnosed by the presence of a conceptus-derived antigen in maternal serum that is secreted by trophoblast and placental tissue primarily as an acidic component of Mr ... [more ▼]

Pregnancy in cattle and sheep can be diagnosed by the presence of a conceptus-derived antigen in maternal serum that is secreted by trophoblast and placental tissue primarily as an acidic component of Mr 67,000. Molecular cloning of its cDNA reveals that the antigen belongs to the aspartic proteinase family and has greater than 50% amino acid sequence identity to pepsin, cathepsin D, and cathepsin E. The inferred sequences of the ovine and bovine polypeptides show approximately 73% identity to each other. Critical amino acid substitutions at the active site regions suggest that both proteins are enzymatically inactive. The antigen is a product of trophoblast binucleate cells that invade maternal endometrium at implantation sites. [less ▲]

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