SP1 Beta Research Articles

Distribution of SP 1, immunoreactivity among different plasma proteins: real molecular heterogeneity or adsorption of SP 1-beta to other plasma proteins?

Three SP 1-containing factors from pooled term pregnancy sera were subjected to crossed immunoelectrophoresis. New patterns as far as electrophoretic mobilities and shapes of the immunoprecipitates were revealed. The appearance of an additional anodic radioimmunoassayable activity in agarose electrophoresis of mixed SP 1-alpha and SP 1-beta suggested a binding capacity of SP 1-alpha for SP 1-beta determinants. In the serum of a single patient at the third trimester of pregnancy we also found two SP 1 variants, possessing little radioimmunological reactivity and with crossed immunoelectrophoretic characteristics quite different from those of the ‘usual’ alpha and beta SP 1 forms. These results suggest that, in this particular case, the overall SP 1 production cannot be evaluated by competitive binding assay and, that in general, SP 1 is a complex antigen the heterogeneity of which can be determined following adsorption of some beta epitopes to another serum protein.

The concentrations of SP1 beta and SP1 alpha in retroplacental and peripheral blood at term.

The concentrations of the two components of Schwangerschaftsprotein 1 (SP1 beta and SP1 alpha), human chorionic gonadotrophin (hCG) and human placental lactogen (hPL), were measured in peripheral venous blood and in retroplacental blood at term delivery in 22 women. Like hCG and hPL, the values of SP1 alpha were higher in the retroplacental than in the peripheral blood, as might be expected with placental secretory products. On the other hand, the concentration of SP1 beta showed a reverse gradient, being higher in the peripheral than in retroplacental blood.

Heterogeneity of the pregnancy-specific β1-glycoprotein (SP1)

The pregnancy-specific beta 1-glycoprotein (SP1) in pregnant serum fractionated by ammonium sulfate precipitation and anion exchange chromatography was investigated by various electrophoretic methods. From these investigations it appears that in addition to the major component SP1(beta) three other components are present, termed SP1(gamma), SP1 (alpha 2(2)) and SP1 (alpha 2(1) on the basis of their electrophoretic mobilities. The isoelectric point (pI), estimated by isoelectric focusing, and the relative molecular mass (Mr), estimated by Sephadex G-200 gel filtration chromatography are for SP1(gamma): pI 2.9--4.9, Mr approximately 80000; SP1(beta): pI 2.5--4.5, Mr approximately 80000; SP1(alpha 2(2)): pI less than or equal to 6, Mr greater than or equal to 200000; SP1(alpha 2(1)): pI less than 3, Mr approximately 30000. Based on the interaction with phenyl-Sepharose and concanavalin A all four species of SP1 are amphiphilic glycoproteins.

An immunochemical study of proteins with SP1 determinants in native and acidified pregnancy serum.

The alpha and beta forms of the pregnancy-associated protein, SP1, have been studied in late pregnancy serum and in similar serum after acidification. In both sera only two forms of the protein, SP1 alpha and SP1 beta, could be found; both reacting with antisera against SP1. On gel chromatography these two forms could be separated, with the intermediate effluent containing a varying mixture of both proteins. Immunoelectrophoresis of the effluent fractions from gel chromatography showed rocket shaped immunoprecipitates whose morphology depended on the mixture of SP1 alpha and SP1 beta. Crossed immunoelectrophoresis confirmed that only two proteins could be defined with SP1 antisera; the front running protein having an alpha 2 electrophoretic mobility and a molecular weight of 430,000, while the slower moving component had the electrophoretic mobility of a beta 1 globulin and a molecular weight of 90,000.

Investigations into the molecular heterogeneity of pregnancy-specific β1-glycoprotein (SP 1)

The molecular heterogeneity of pregnancy-specific beta 1-glycoprotein (SP1) was examined by analytical immunoelectrophoresis and a radioimmunostaining technique of immunoelectrophoretic plates. Analytical crossed immunoelectrophoretic analysis and radioimmunostaining of these plates demonstrated the presence of normal human serum components in the alpha-mobile precipitate previously considered to be exclusively the high molecular pregnancy-specific protein, SP1 alpha. This observation suggested that two molecular populations were contributing to the alpha-mobile precipitate. Following fractionation of late-pregnancy serum by size chromatography, the radioimmunostaining technique further demonstrated the presence of normal serum components in the intermediate fraction but not in authentic SP1 (i.e., SP1 beta) or the high molecular weight form (SP1 alpha). We suggest that SP1 antigenic determinants are distributed in three different fractions of pregnancy serum, one of which (intermediate fraction) is a complex of authentic SP1 (SP1 beta) and a normal serum protein, whereas non-pregnancy serum components were not demonstrable in the remaining two (i.e., SP1 beta or SP1 alpha).

Observations on the separation of SP 1α and SP 1β by affinity chromatography

SP1 antigens in late pregnancy blood, in placental extracts and in acidified plasma have been purified on positive affinity chromatography columns with immobilized SP1 antiserum and on negative affinity columns with immobilized antihuman non-pregnancy serum. Both SP1 alpha and SP1 beta are bound by the positive column but only SP1 alpha is bound by the negative column. This is adduced as further support for the view that SP1 alpha is formed by the combination of SP1 beta with a protein present in non-pregnancy serum.

Human in vitro fertilisation and embryotransfer: first results at the 2nd department of obstetrics and gynaecology, university of vienna (author's transl)

Methods and Results of human in vitro fertilisation at the 2nd Department of Obstetrics and Gynaecology, University of Vienna are reported. Applying preparations of media and culture techniques according to Edwards et al. no satisfactory results could be achieved: only 3 out of 11 preovulatory oocytes were fertilised, no cleavages occurred. Using modified Ham's F 10 medium according to Lopata et al. fertilisation could be observed in 60% as well as regular cleavages in 40%. 5 Embryotransfers have been performed in the 8 cell or in the 16 cell stage respectively. No implantation occurred in 4 of these, in one case evidence for a transient implantation could be proved by an increased activity of SP1 and HCG beta. In this case obviously postimplantation death occurred resulting in a bleeding 16 days after oocyte recovery. Possible reasons for failures in fertilisation and cleavage as well as possibilities for improving the rate of reimplantation are discussed.

Separation of two pregnancy-associated proteins with SP1 determinants and the conversion of SP1 beta to SP1 alpha.

The alpha and beta forms of the pregnancy-associated protein, SP1 which have been previously identified in late pregnancy serum were found to be also present in the placenta. The alpha form was somewhat more difficult to extract, requiring the use of detergents in the extracting buffer. The two variants can be separated by ion exchange chromatography or by gel filtration and distinguished by the different shapes of the precipitation rockets on immunoelectrophoresis. The alpha variant appears to be the larger molecule on gel filtration. When solutions of SP1 are acidified to pH 2.5 the beta form is rapidly converted to the alpha form and the latter is slowly destroyed. It is suggested that SP1 alpha represents the combination of SP1 beta with some other protein present in the placenta and in the serum.

The ratio between molecular variants of pregnancy-specific β1 glycoprotein (SP 1) in the peripheral and retroplacental circulation during late pregnancy

The ratio between two molecular variants of pregnancy-specific beta 1 glycoprotein (SP1) in the peripheral and retroplacental circulation was analysed in nine women during late pregnancy. The ratio between the two molecular variants, i.e. SP1 beta and SP1 alpha, was found to be identical in the peripheral and retroplacental circulation in all women examined. Comparisons were also made between SP1 beta as measured by radioimmunoassay and a normal serum protein, alpha 2 macroglobulin. A positive concentration gradient from peripheral to retroplacental circulation was found for SP1 beta whereas the gradient was less pronounced for alpha 2 macroglobulin. These findings add weight to the concept that SP1 alpha is a unique molecular species and not a genetic variant or a product of SP1 beta.