Placental localization of human pregnancy--associated plasma proteins

Seminal plasma levels of PAPP-A in normospermic and oligospermic men and tissue localization of PAPP-A in the male genital tract

Radioimmunoassay, gel filtration, isoelectric focusing, and immunoperoxidase methods were used to study the levels, properties, and localization of pregnancy-associated plasma protein A (PAPP-A) in the human seminal plasma and male genital tract. Seminal plasma specimens from 20 normospermic and 20 oligospermic men were studied. PAPP-A was found in 30 of 40 samples, the levels ranging from undetectable to 135 micrograms/liter (median 35 micrograms/liter) in the normospermic group and from undetectable to 111 micrograms/liter (median 21 micrograms/liter) in the oligospermic group. There was no significant difference in the PAPP-A levels between the two groups, and no correlation was observed between the seminal plasma PAPP-A levels and the volume of seminal plasma or the sperm count or the viability of spermatozoa. Serial dilutions of seminal plasma and PAPP-A standard yielded parallel dose-response curves, and incubation with seminal plasma did not result in any change in the elution pattern of [125I]PAPP-A in gel filtration. PAPP-A-immunoreactive material from seminal plasma eluted as two peaks, the major one corresponding to the elution volume of purified PAPP-A and the minor eluting more slowly. The isoelectric point of seminal plasma PAPP-A was 4.3-4.7 and that of term pregnancy serum was 4.2-4.6. In the immunoperoxidase staining, PAPP-A was seen in the epithelium of the prostate, seminal vesicle, and the ampullar part of the vas deferens but not in the testis, epididymis, proximal parts of vas deferens or urethra. The results confirm the occurrence of PAPP-A in the seminal plasma but do not suggest any clinical utility for seminal plasma PAPP-A measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial primary structure of human pregnancy zone protein: extensive sequence homology with human alpha 2-macroglobulin

Human pregnancy zone protein (PZP) is a major pregnancy-associated protein. Its quaternary structure (two covalently bound 180-kDa subunits, which are further non-covalently assembled into a tetramer of 720 kDa) is similar to that of human alpha 2-macroglobulin (alpha 2M). Here we show, from the results of complete or partial sequence determination of a random selection of 38 tryptic peptides covering 685 residues of the subunit of PZP, that PZP and alpha 2M indeed are extensively homologous. In the stretches of PZP sequenced so far, the degree of identically placed residues in the two proteins is 68%, indicating a close evolutionary relationship between PZP and alpha 2M. Although the function of PZP in pregnancy is largely unknown, its close structural relationship to alpha 2M suggests analogous proteinase binding properties and a potential for being taken up in cells by receptor-mediated endocytosis. In this regard our studies indicate a bait region in PZP significantly different from that present in alpha 2M. PZP could be the human equivalent of the acute-phase alpha-macroglobulins (e.g., rat alpha 2M and rabbit alpha 1M) described earlier.

Serum concentration of pregnancy-associated plasma protein A in the first trimester of pregnancy

Serial assays of pregnancy-associated plasma protein A were done in 12 subjects before the first missed menstrual period through 10 to 16 weeks' gestation. It was found that the concentration of pregnancy-associated plasma protein A remained at prepregnancy levels until 6 to 10 weeks after the last menstrual period. Thereafter the concentration increased rapidly. It is surmised that pregnancy-associated plasma protein A is a maternal protein, the synthesis of which is stimulated by pregnancy.

Observations on the source of pregnancy-associated plasma protein A (PAPP-A)

Pregnancy-associated plasma protein A (PAPP-A) was measured in 26 women before and after hysterectomy. The PAPP-A concentration declined significantly in 24 of them. It is concluded that the uterus is a source of the protein.

The localization of pregnancy proteins (hPL, SP1 and PAPP-A) in intra- and extrauterine pregnancies

The localization of human placental lactogen (hPL), pregnancy-specific beta-1 glycoprotein (Schwangerschaftsprotein 1, SP1) and pregnancy-associated protein A (PAPP-A) was examined in intrauterine and tubal ectopic gestation (n = 5) by the immunoperoxidase technique. The distribution of hPL and SP1 was identical in placental tissues obtained from intra- and extrauterine pregnancies, being uniformly seen throughout the syncytiotrophoblast. hPL and SP1 were not demonstrated in uterine decidual tissue from ectopic pregnancies. During early (week 8) intrauterine pregnancy, PAPP-A was not restricted to the mature syncytiotrophoblast, being observed also in some trophoblast-like cells adjacent to islands of syncytiotrophoblast. In contrast, in ectopic gestation, PAPP-A was observed in these cells at six weeks' gestation only. We were unable to detect PAPP-A in trophoblastic tissue of chorionic villi and uterine decidual tissue from ectopic gestation.

SP-I secretion by baboon embryos in vitro

Baboon embryos cultured to postimplantation stages have been shown to secrete the placental protein SP-I into the culture medium in quantities of up to almost 5 micrograms/day, based on a rhesus monkey standard. Twelve embryos, for which spent media samples have been assayed, have been shown to secrete this protein, with measurable quantities usually being present on day four following attachment of the zonaless embryo to the culture dish. Secretion has continued for up to 14 days, with over 26 micrograms total SP-I secretion from one embryo. These observations further enhance the utility of the baboon embryo culture system as a model for studying early placental development in the primate.

Immunohistochemical demonstration of pregnancy-associated plasma protein A (PAPP-A) in the syncytiotrophoblast of the normal placenta at different gestational ages

The immunoperoxidase technique was used to study the localization of pregnancy-associated plasma protein A (PAPP-A) in formaldehyde-fixed paraffin-embedded tissue from normal human placentae at the gestational age of 8, 15 and 40 weeks. Sections of formaldehyde-fixed tissue treated with a proteolytic enzyme and incubated in antiserum against PAPP-A either raised in goats or rabbits showed that PAPP-A was distributed in the cytoplasm of the syncytiotrophoblast. The protein was not found in the cytotrophoblast. Sections without pretreatment with trypsin and incubation in goat anti-PAPP-A showed no staining reaction, whereas incubation in rabbit anti-PAPP-A revealed a staining of the syncytiotrophoblast surface. The results indicate that PAPP-A is probably synthesized in the syncytiotrophoblast.

Pregnancy-associated plasma protein-A (PAPP-A): concentration in uterine fluid and immunohistochemical localization in the endometrium

Pregnancy-associated plasma protein-A (PAPP-A) was localized immunohistochemically in the endometrium and measured in uterine fluid of non-pregnant women. The variations of PAPP-A concentrations in uterine fluid during the menstrual cycle paralleled those found in the endometrium. In patients receiving hormone therapy there was a significant correlation between the uterine fluid PAPP-A concentration and the progestogen to oestrogen potency ratio of the hormonal treatment. The presence of PAPP-A in the uterine fluid cannot simply be explained by blood contamination or cell damage. These results are interpreted as indirect evidence for an exocrine as well as an endocrine secretion of PAPP-A by the endometrium which might be influenced by hormones.

An immunohistological comparison of the secretory capacity of villous and extravillous trophoblast in the human placenta

Using an immunoperoxidase technique the localization of hCG, hPL, SP1, PAPP-A and PP5 within villous and extravillous trophoblast has been studied. The villous syncytiotrophoblast appears to be the sole significant source of hCG, SP1, PAPP-A and PP5 but hPL is also present in the infiltrating extravillous trophoblast. Within the interstitial extravillous trophoblast the proportion of cells staining positively for hPL increases progressively as the cells extend deeper into the uterine tissues but all the vascular extravillous trophoblast within the lumina of the spiral arteries stains positively for hPL at all levels within the decidua and inner myometrium. It is not clear why the synthetic capacity of the infiltrating trophoblast is limited to the production of hPL. We suggest that this might be indicative of selectivity of a specific subpopulation of cytotrophoblastic cells. It is unlikely that the physiological effects of infiltrating trophoblast are mediated by hPL, this substance being probably only a marker of a cell population with a particular invasive capacity.

Immunohistochemical localization of pregnancy-associated plasma protein A (PAPP-A) in placentae from normal and pre-eclamptic pregnancies

An immunohistochemical method was used to locate pregnancy-associated plasma protein A (PAPP-A) in the placenta and uterus. In addition to 10 placentae and basal plates from normal pregnancies, ranging in gestational age from 37 to 40 weeks, the following specimens were studied: three uteri obtained by hysterectomy during early pregnancy; and three placentae from patients with severe hypertensive pre-eclampsia. In early gestation, PAPP-A was localized in the villous cytotrophoblastic cell layer and the endometrial glands but was not found in the villous syncytiotrophoblast, the cytotrophoblastic cell columns or the decidual cells. On histochemical examination of placentae from cases of pre-eclampsia with hypertension, an increased number of villous cytotrophoblastic cells and so-called X-cells was observed. The monospecific antiserum to PAPP-A reacted strongly and evenly with the cytoplasm of these cells. The present study strongly suggests that the active production sites of PAPP-A are the villous cytotrophoblastic cells and the X-cells.

Immunohistochemical localization of pregnancy-associated plasma protein A in decidua and trophoblast: comparison with human chorionic gonadotrophin and fibrin

In an immunoperoxidase study, pregnancy-associated placental protein A (PAPP-A) was localized to the cytoplasm of decidual stromal cells, the villous syncytiotrophoblast and on the surface of placental trophoblast. A decidual and a trophoblastic origin is suggested for PAPP-A, and its presence on the surface of the syncytiotrophoblast is interpreted as a possible immunoprotective layer.

Pregnancy-associated plasma protein A (PAPP-A) in non-pregnant subjects

A newly developed enzyme immunoassay technique was applied to the measurement of pregnancy-associated plasma protein A (PAPP-A) in the serum of women in the proliferative and luteal phases of the cycle, in hysterectomized and postmenopausal women and in the serum and seminal plasma of males. PAPP-A was detected in some individuals in all the categories of women and in seminal plasma but not in male serum. It is surmised that there must be a source of PAPP-A other than the placenta and that PAPP-A may be a maternal protein whose biosynthesis is stimulated by pregnancy rather than a product peculiar to the trophoblast.

Hyperstimulated human preovulatory follicular fluid, luteinized cells of unruptured follicles, and corpus luteum contain pregnancy-associated plasma protein A (PAPP-A)

Radioimmunoassay, gel filtration, and immunoperoxidase methods were used to study the occurrence, properties, and concentration of pregnancy-associated plasma protein A (PAPP-A) in the human ovary and in the follicular fluid from 97 hyperstimulated follicles from 29 infertile women participating in an in vitro fertilization program. At the detection level of 15 micrograms/l, PAPP-A was found in 83 of 97 follicular fluids, the levels ranging from undetectable to 483 micrograms/l (median, 130 micrograms/l). In gel filtration, PAPP-A immunoreactivity of follicular fluid eluted in the same volume as placental PAPP-A, and the dose-response curves of follicular fluid PAPP-A and purified PAPP-A were parallel. The PAPP-A concentration was not affected by prior treatment with a protease inhibitor. Follicular fluid aspirates containing the ovum had a higher PAPP-A concentration than those in which no ovum was detected (P less than 0.01), whereas no difference was found in the PAPP-A concentrations between follicles yielding an ovum which was fertilized and cleaved and those yielding an unfertilizable oocyte. There was a correlation between PAPP-A and estradiol or progesterone concentrations, and between the PAPP-A concentration and the volume of follicular fluid aspirate. In hyperstimulated unruptured follicles, PAPP-A was localized in the luteinized granulosa and theca interna cells, but not if luteinization was not observed. Corpus luteum cells were also PAPP-A positive, whereas unstimulated Graafian follicles were negative. Our results indicate that PAPP-A appears in the hyperstimulated follicle shortly before ovulation and may thus play a part in the early events of human reproduction.

In vitro production of pregnancy-associated plasma protein A by human decidua and trophoblast

Immunohistochemical techniques and direct measurements of pregnancy-associated plasma protein A (PAPP-A) have demonstrated the presence of PAPP-A in trophoblast and decidua. The purpose of the present study was to investigate the possibility that these tissues are capable of producing PAPP-A in vitro. Trophoblast and decidua were obtained from term deliveries and from legal surgical terminations of pregnancy (7 to 12 weeks). In addition to trophoblast and decidua, myometrium was also obtained during two hysterectomies in the first trimester of pregnancy. Tissues were incubated in medium 199 at 37 degrees C under an oxygen/carbon dioxide atmosphere. Media containing either pregnancy-associated serum or non-pregnancy-associated serum were changed after 8 hours of incubation in medium 199 alone. In addition to PAPP-A, human placental lactogen (hPL) and prolactin (Prl) were measured in homogenates and media by radioimmunoassays in order to confirm the viability of the cultured tissues. Addition of pregnancy-associated serum to the media induced a significant release of PAPP-A from trophoblast and decidua when compared to that in control cultures. Non-pregnancy-associated serum had no effect. Myometrium did not release any measurable PAPP-A into the medium even in the presence of pregnancy-associated serum. Cycloheximide added to pregnancy-associated serum significantly inhibited the release of PAPP-A from trophoblast and decidua. These last tissues, irrespective of the culture condition, released significantly more PAPP-A as well as hPL and Prl than was initially present in the tissue. These data demonstrate that PAPP-A is released in vitro by trophoblast and decidua (but not by myometrium) and that this release can be magnified by a factor present only in pregnancy-associated serum. The release of PAPP-A, hPL, and Prl is considered as a de novo production since concentration of these proteins are higher in media and tissues after incubation compared to concentrations initially present in the tissue before culture and since cycloheximide significantly inhibits the release of PAPP-A, Prl, and hPL from the cultured tissues.

Pregnancy-associated plasma protein A (PAPP-A) specifically inhibits the third component of human complement (C3)

Pregnancy-associated plasma protein A (PAPP-A), a macromolecular glycoprotein associated with pregnancy, was shown to inhibit complement-induced haemolysis and to bind heparin reversibly. Because of the inhibitory effects of heparin on the complement cascade it was not clear if the inhibition of complement activity observed with PAPP-A (isolated from heparin plasma) was attributable to the heparin moiety bound to PAPP-A. This work demonstrates that heparin exerts an inhibitory effect on complement activity but that heparin-free PAPP-A is also inhibitory. PAPP-A specifically inhibits C3 by binding to this complement subcomponent and not by inhibiting C3 convertase as demonstrated for C3 inactivator.

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.

Diagnosis of early pregnancy by assay of placental proteins

The plasma concentrations of Schwangerschaftsprotein 1 (SP1) and human chorionic gonadotrophin (hCG) were measured in 22 women before and after conception. In these pregnancies ovulation occurred spontaneously in seven subjects, or followed treatment with either clomiphene citrate (6 subjects), or human menopausal gonadotrophin (hMG) and hCG (6 subjects). The remaining three patients became pregnant after artificial insemination with donor semen. Seventeen of these pregnancies were normal and five were abnormal (3 abortions, 1 ectopic and 1 twin). SP1 could be detected 6-14 days after ovulation in all these patients. In contrast 40 non-pregnant women gave a negative test for SP1.

In vitro translation of human placental pregnancy-specific beta 1-glycoprotein (SP1)

Synthesis of SP1-glycoprotein by the human placenta was directly demonstrated, by in vitro translation of RNA extracted from full term and from early placentas in a cell-free wheat germ system followed by specific immunoprecipitation of the radioactively labeled nascent peptides. De novo synthesized SP1-glycoprotein in both RNA preparations accounted for 1-1.3% of total protein synthesis.

Specific and reversible interaction between pregnancy-associated plasma protein A and heparin

An interaction between heparin and circulating pregnancy-associated plasma protein A (PAPP-A) has been observed. This interaction could be reversed by the addition of the specific heparin antagonist protamine sulphate. In the presence of heparin, crossed immunoelectrophoretic analysis revealed an alteration in the electrophoretic mobility of PAPP-A, while a significant increase (22 to 64 per cent, P less than 0.02) in measured levels of PAPP-A was seen in electroimmunoassays. These findings are discussed in relation to the optimal conditions for the precise measurement of PAPP-A.

Development of a radioimmunoassay for pregnancy-associated plasma protein A and establishment of normal levels in the first trimester of pregnancy

An accelerated double antibody method has been developed for the radioimmunoassay of pregnancy-associated plasma protein A (PAPP-A) in serum. The workable range for the assay was 0.04-1.8 mg/l of serum. PAPP-A levels were determined in single serum samples from 110 women with prospective normal pregnancies of between 7 and 14 weeks' gestation. The level of pregnancy specific beta 1 glycoprotein (SP1) was also measured in these samples and normal ranges for PAPP-A and SP1 were constructed from the results obtained.

Endometrial and plasma concentrations of pregnancy-associated plasma protein-A (PAPP-A)

Pregnancy-associated plasma protein-A (PAPP-A), oestradiol and progesterone levels have been measured by radioimmunoassay in plasma and in endometrial homogenates of 20 women undergoing hysterectomy. Results were grouped according to the histological stages of the endometrium. In plasma, oestradiol and progesterone concentrations changed from proliferative to secretory stages in the well-established pattern of the menstrual cycle, but PAPP-A levels did not change. In endometrium, oestradiol levels were high during the proliferative stage and low in inactive and secretory endometrium. Endometrial PAPP-A and progesterone concentrations increased from inactive to secretory stages, but only the increase in PAPP-A was statistically significant. A positive correlation observed between endometrial PAPP-A concentrations and plasma oestradiol/progesterone ratio suggests a possible hormonal control for the presence of PAPP-A in the uterus.

Is pregnancy-associated plasma protein A a tumor marker?

Pregnancy-associated plasma protein A (PAPP-A) was measured in 159 patients with various nontrophoblastic tumors. In three patients with trophoblastic tumors, PAPP-A and human chorionic gonadotropin (hCG) were measured before operation and weekly thereafter. Circulating levels of PAPP-A in patients with nontrophoblastic tumors were not significantly different from the levels in the matched control groups. Circulating levels of PAPP-A and hCG were significantly elevated preoperatively in patients with trophoblastic tumors, whereas the postoperative concentrations of both proteins gradually decreased. The conclusion is that, probably, PAPP-A cannot be considered to be a marker for nontrophoblastic disease, and that measurements of PAPP-A in patients with trophoblastic cancers do not provide any advantage over measurements of hCG.

Tissue and plasma concentrations of pregnancy-associated plasma protein-A (PAPP-A): comparison with other fetoplacental products

Human placental lactogen (hPL), alpha fetoprotein (AFP), prolactin (PRL) and pregnancy-associated plasma protein-A (PAPP-A) were measured by radioimmunoassay in plasma, in homogenates of trophoblast, decidua, chorion, amnion and in amniotic fluid from 10 patients after non-complicated term delivery. Plasma samples and homogenates of trophoblast and decidua were also collected from 10 patients undergoing surgical termination of pregnancy between 7 and 12 weeks gestation. In addition, plasma and endometrial samples from 10 patients undergoing hysterectomy for other indications than malignancy were analysed for comparison. The highest tissue concentrations of hPL, AFP and PRL corresponded in each case to the known site of synthesis. For PAPP-A the highest concentration was found in maternal plasma at term [238.8 +/- 75.6 (SEM) micrograms/ml]. The highest tissue concentration was found at term in the decidua (57.0 +/- 2.0 micrograms/g), more than three times higher than that in the trophoblast (16.9 +/- 5.4 micrograms/g). The concentrations of PAPP-A in endometrial samples from non-pregnant women (1.9 +/- 0.6 micrograms/g) was 40 times higher than that in the corresponding plasma samples (0.05 +/- 0.02 microgram/ml). These observations point to the decidua as a possible source of PAPP-A.

Amniotic fluid and plasma concentrations of pregnancy-associated plasma protein-A (PAPP-A) throughout pregnancy: comparison with other fetoplacental products

The development of a sensitive radioimmunoassay has enabled measurements of pregnancy-associated plasma protein-A (PAPP-A) to be performed from early pregnancy. The present paper compares the plasma concentrations of PAPP-A with the levels of two trophoblastic proteins, human placental lactogen (hPL) and the beta-subunit of human chorionic gonadotrophin (beta-hCG), with a steroid of fetoplacental origin, total oestriol (total E3), and with a fetal protein, alpha-fetoprotein (AFP). PAPP-A was also measured in amniotic fluid and in maternal urine. In contrast with the secretion of the other substances studied, which either reach a plateau or even decrease during the last 4 weeks of pregnancy, PAPP-A steadily increased in the maternal circulation from 7 to 40 weeks gestation. It is proposed that PAPP-A production is either not related to placental mass or that PAPP-A is not of trophoblastic origin. The increase of PAPP-A in amniotic fluids parallels the increase in maternal blood; virtually no PAPP-A is excreted in urine.

Studies on the concentration of pregnancy-associated plasma protein-A during normal and complicated pregnancy

Pregnancy-associated plasma protein-A was assayed in the blood of 347 women during pregnancy, using a new primary standard of PAPP-A as reference. The protein was assayed by antibody-antigen crossed electrophoresis with the lower limit of confident assay being 9.5 micrograms PAPP-A/ml (13 pmol/ml). PAPP-A was first detected at 14 weeks of gestation; by term it had risen to within the range 20 to 320 micrograms/ml. There was an indication that pregnancies involving a male baby had higher PAPP-A levels in blood than did those involving female babies. In 51 blood samples from 30 patients with gestational diabetes (taken between 28 weeks of pregnancy and term) there was no significant alteration in PAPP-A values compared with controls. In 35 blood samples from 15 patients with insulin-dependent diabetes, levels of PAPP-A were significantly lower than in controls or in gestational diabetes. In 43 blood samples from 35 patients with babies affected with intrauterine growth retardation (between 28 weeks and term), there was no significant difference in PAPP-A levels compared with controls. The effect of insulin on the blood levels of PAPP-A suggests that the concentration of PAPP-A is capable of altering significantly in response to certain physiological changes associated with the control of carbohydrate metabolism.

Pregnancy-associated plasma protein-A (PAPP-A) and hCG in early pregnancy

Pregnancy-associated plasma protein-A (PAPP-A) is a recently described glycoprotein of unknown biological function. The development of a radioimmunoassay enabled us to measure plasma levels of PAPP-A and human chorionic gonadotrophin (hCG) in 12 non-pregnant volunteers and in 159 women in early pregnancy attending the outpatient clinic for legal abortion. PAPP-A but not hCG was measurable in all non-pregnant women. In pregnant patients (with 36 to 86 days of amenorrhea) hCG reached a peak value (163.1-197.6 ng/ml) between the 9th and the 13th week whereas PAPP-A steadily increased throughout this period of pregnancy. Between the 6th and the 13th week after the last menstrual period, levels of PAPP-A increased proportionally more than hCG. This work provides the first evidence of a PAPP-A production in non-pregnant subjects and the very early marked increase of PAPP-A secretion during pregnancy.

Pregnancy-associated plasma protein A: circulating levels during normal pregnancy

The development of specific and sensitive electroimmunoassays for a recently identified high molecular weight alpha-2 mobile pregnancy-specific protein (pregnancy-associated plasma protein A, PAPP-A or SP4) is described. These assays have permitted the detection of circulating levels of PAPP-A (10 microgram/L) as early as the fifth week of pregnancy. In all 18 subjects studied, the levels of PAPP-A rose from first detection in the first trimester until delivery at term. The development of these assays now permit the evaluation of PAPP-A measurement as a diagnostic test of early pregnancy and as an index of fetal well-being throughout gestation.

Purification of pregnancy-associated plasma protein-A by a two step affinity chromatographic procedure

A high molecular weight pregnancy specific protein (PAPP-A) was purified by immunospecific affinity chromatography. The purification procedure was based on a new method for affinity chromatography using direct coupling of precipitable immune complexes to the gel matrix. The procedure was performed in two steps: a positive immunospecific affinity chromatography followed by a negative affinity chromatography in which balanced amounts of anti-contaminant antibodies were used as ligant. The purified material at a concentration of 300 microgram/ml was tested by immunoelectrophoretic methods and no contaminants were detectable. WHO beta-1 SP1 reference material 78610 contained 45 microgram PAPP-A/ml.

Pregnancy-associated plasma protein-A: an inhibitor of the complement system

Pregnancy-associated plasma protein-A (PAPP-A) was purified to homogenicity from third-trimester pregnancy plasma using ion exchange chromatography and affinity chromatography on con A-Sepharose and anti-human serum-Sepharose. The elution of PAPP-A, alpha 2-macroglobulin, Cl-inhibitor and alpha 1-antitrypsin was followed by immuno-diffusion. the eluates were tested for stimulation or inhibition of complement-induced haemolysis. PAPP-A markedly inhibits the haemolytic activity of complement.

Placenta-associated plasma protein-A (PAPP-A, SP4) in trophoblastic tumours

The immunoperoxidase technique was used to study the occurrence of placenta-associated plasma protein A (PAPP-A, SP4) in formalin-fixed paraffin-embedded tissue specimens from 15 hydatidiform moles, 6 invasive moles and 7 choriocarcinomas. PAPP-A was found in the syncytiotrophoblast of all hydatidiform moles, in 5 of the 6 invasive moles and in 6 of the 7 choriocarcinomata. No clinical difference was observed between PAPP-A positive and negative cases of invasive disease.

Interrelationships of human chorionic gonadotropin, human placental lactogen, and pregnancy-specific beta 1-glycoprotein throughout normal human gestation

Human chorionic gonadotropin (hCG), human placental lactogen (hPL), and pregnancy-specific beta 1-glycoprotein (PSBG) were measured by radioimmunoassay in 270 samples of serum from women with uncomplicated pregnancies. All three proteins were significantly correlated with each other in individual samples of serum and with the estimated trophoblastic mass during the first trimester. No significant correlation could be demonstrated between the concentrations of hCG and PSBG in maternal serum during the second or third trimesters or between the concentrations of hCG and hPL during the second trimester. Levels of PSBG and hPL in serum were significantly correlated throughout all three trimesters. These findings suggest that the secretion of hCG, hPL, and PSBG may be regulated by similar control mechanisms during the first trimester of pregnancy. However, after this period, the factors that modulate the production of hCG differ from those that regulate the production of hPL and PSBG.

Studies on human pregnancy-associated plasma protein A. Purification by affinity chromatography and structural comparisons with alpha 2-macroglobulin

Pregnancy-associated plasma protein-A (PAPP-A) has been purified by a combination of methods including antibody-affinity chromatography. The resultant protein, obtained in 16% yield from maternal serum, appeared as a single major component on non-denaturing polyacrylamide and SDS/polyacrylamide gel electrophoresis. The protein showed a single component when analysed by isoelectric focusing under denaturing conditions in the presence and absence of reduction and had a pI of 4.34 and 4.42 respectively. These pI values were indistinguishable from those of alpha 2-macroglobulin (alpha 2M). The molecular weight of the PAPP-A polypeptide as shown by SDS/polyacrylamide-gel electrophoresis was 187000, with a minor component of mol.wt. 82500 that was attributed to proteolysis. Since native PAPP-A had a molecular weight on gel chromatography very similar to that of alpha 2M (620000--820000), it was concluded that PAPP-A was a homotetramer. In the absence of reduction, a high-molecular-weight (420000) protomer of PAPP-A was found. It was deduced that PAPP-A, like alpha 2M, is a dinner, whose protomers are composed of disulphide-linked polypeptide chains. It was found that the molecular weight of the PAPP-A polypeptide exceeded that of alpha 2M by 3.3%, but that the total carbohydrate content of PAPP-A exceeded that of alpha 2M by 10% and that its neutral carbohydrate content exceeded that of alpha 2M by between 7.4 and 9.0%. The significance of the estimated molecular weights of alpha 2M (181000) and its major tryptic fragments is discussed in the light of published values. A tryptic fragment alpha 2M (82500 mol.wt.) was apparently the same size as the major tryptic fragment of PAPP-A.

Relationship of obstetric parameters to the concentration of pregnancy-associated plasma protein A

Pregnancy-associated plasma protein A (PAPP-A) was measured by rocket immunoelectrophoresis in 272 patients at 34 weeks of pregnancy and within 48 hours before delivery. The values obtained have been compared to maternal parameters (age, weight, weight gain, blood group, rhesus factor, and parity) and to fetal parameters (sex, weight, Apgar score, rhesus factor, blood group, and placental weight). Maternal age, increased parity, and increased body weight are related to decreased PAPP-A levels. On the other hand, mothers carrying male fetuses, rhesus-negative children, and babies with Apgar scores higher than 7 at 1 minute have increased PAPP-A concentrations. These findings are discussed in relation to PAPP-A's involvement in the maternal immunologic system.

Neuronal loss in hippocampus induced by prolonged ethanol consumption in rats

Quantitative neurohistological techniques were used to examine the hippocampal complex of laboratory rats maintained on ethanol-containing or control diets for 5 months followed by a 2-month alcohol-free period. Chronic ethanol consumption resulted in a significant loss of hippocampal pyramidal and dentate gyrus granule cells. This study provides direct evidence that long-term ethanol consumption, in the absence of malnutrition, produces neuronal loss in the central nervous system.

[The influence of mode of delivery on retroplacental and peripheral serum concentrations of HPL and SP-1 (author's transl)]

The concentrations of HPL and SP-1 were measured in retroplacental and peripheral serum in patients who had an elective Caesarean section and in patients who had a spontaneous vaginal delivery. The peripheral concentration of HPL was significantly lower after vaginal delivery than after elective Caesarean sections (p < 0.001). The retroplacental concentration of serum-SP-1 after vaginal delivery was significantly higher than after elective Caesarean section (p < 0.001). After elective Caesarean section the retroplacental concentration of SP-1 was significantly lower than the peripheral concentration (p < 0.001), but after vaginal delivery the mean retroplacental and peripheral serum-SP-1 values were about equal.

Assay of a placental protein to determine fetal risk

Plasma concentrations and total amounts of pregnancy associated plasma protein A were determined in 272 patients at 34 weeks' gestation by immunoelectrophoretic assay. The mean plasma concentration and mean total amount of this protein were closely related (r = 0.9643) and were significantly raised in patients who subsequently developed pre-eclampsia (28 patients), went into premature labour (12), or suffered from antepartum haemorrhage (10). Mean values in all patients delivering growth-retarded babies were also raised, but when the results for such patients who also had other complications were excluded there were no differences between the sets of means. The assays were easily performed, and they may be a useful technique for screening pregnant women to detect those at risk of developing pre-eclamptic toxaemia, although the full potential of these assays cannot be realised until the protein's function is known.

Migration of binucleate cells in the sheep placenta during normal pregnancy

The maternofetal interface in the placentomes of the sheep placenta consists of a fetal cellular chorion layer whose apical microvilli interdigitate with those of a syncytial layer which borders the maternal connective tissue. Most of the granulated binucleate cells found in the chorion epithelium reach neither its basement membrane nor its microvillar junction apex. However, up to one fifth of the binucleate cells can be shown to be part of or push pseudopodia across the microvillar junction or are located within the syncytium. The syncytium and chorionic binucleate cells both have a nuclear chromatin structure and distinctive cytoplasmic granules which are not found in any other placental cells. This suggests that most, if not all, of the syncytium is derived by fusion of fetal binucleate cells which have migrated across the microvillar junction from the chorion, and that the immunological maternofetal junction does not lie between chorion and syncytial layers.

Purification and characterization of pregnancy associated plasma protein A (PAPP-A)

Pregnancy Associated Plasma Protein A (PAPP-A) has been isolated from late pregnancy plasma using ammonium sulphate precipitation, ion exchange chromatography, affinity chromatography on Concanavalin-A, gel filtration and negative affinity chromatography. It was found that PAPP-A is an alpha 2-glycoprotein of 750-820 000 MW, probably a dimer with each monomer being composed of 2 polypeptide chains of 218 000 MW. The amino acid composition as well as other physicochemical characteristics are similar to human alpha 2-macroglobulin. PAPP-A exhibits in vitro an inhibition of the activity of the complement system, of the caseinolytic activity of plasmin and possibly of the urokinase activation of plasminogen. The hypothesis that PAPP-A plays a role in the regulation of fibrinolysis during pregnancy is put forward.

Studies on pregnancy-associated plasma protein A in the third trimester of pregnancy

The plasma concentration of pregnancy-associated plasma protein A (PAPP-A) was measured in 34 women during the last 10 weeks of pregnancy. From 30 to 36 weeks the concentration of this protein increased steadily. Thereafter the concentration of PAPP-A rose more steeply, the highest amounts being found in early labour. The concentration of PAPP-A in peripheral venous blood and in the uterine vein was much the same. It was less in the retroplacental blood and a great deal less in the peritoneal fluid. The day-to-day variation was small; the coefficient of variation at 38 weeks was only 7.3 per cent. After delivery, the concentration of PAPP-A fell more slowly than other placental proteins and steroids, the average half-life being 51 hours. Although there is no doubt that PAPP-A is a product of the syncytiotrophoblast, our findings suggest that it is not simply secreted by the chorionic villi directly into the intervillous space but makes its way into the maternal circulation by a more circuitous route.

The value of measurement of pregnancy-specific proteins in twin pregnancies

In this study of 53 twin pregnancies, the plasma concentrations of the placental proteins, placental lactogen (hPL), and pregnancy-specific glycoprotein (SP1) were measured. Placental lactogen was found to be of more value than SP1 both in the detection of twins and in assessment of fetal growth. Serial measurement of either protein would seem to be more useful in assessment of fetal growth than single measurements. Preliminary studies of the less well known placental protein, PP5, in a small series of twin pregnancies indicate that it may also prove to be of clinical value in the detection and monitoring of twin pregnancies.