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The uptake of polyunsaturated fatty acids by rat hepatoma cells and fetal hepatocytes has been studied using albumin and alpha-fetoprotein (AFP) as carrier proteins. Both types of cells took up linoleic (18:2(n-6)) and linolenic (18:3(n-3)) fatty acids at the same rate when they were added complexed either to albumin or AFP at a 1:1 molar ratio. At 37 degrees C a greater incorporation of arachidonic acid (20:4(n-6)) and mainly docosahexaenoic acid (22:6(n-3)) was observed when these acids were bound to albumin (6.5 nmol 20:4(n-6); 6.4 nmol 22:6(n-3) /million cells) as compared to AFP (5.5 nmol 20:4(n-6); 4.3 nmol 22:6(n-3)/million cells). The 20:4(n-6) and 22:6(n-3) uptake seems to be inversely related to the apparent association constants (k'a) between these fatty acids and both proteins (1.3 and 1.5 x 10(-7) M-1 20:4(n-6) and 22:6(n-3) for albumin; 6.4 and 54.0 x 10(-7) M-1 20:4(n-6) and 22:6(n-3) for AFP). Experiments carried out at 4 degrees C indicated that binding of 20:4(n-6) (0.83 nmol/million cells in presence of albumin; 2.16 nmol/million cells in presence of AFP) and 22:6(n-3) (0.83 nmol/million cells in presence of albumin; 1.32 nmol/million cells in presence of AFP) by cell membranes was also inversely related to the k'a of these proteins. At 4 degrees C, the k'a of AFP and albumin for 20:4(n-6) and 22:6(n-3) changed considerably (12.7 and 9.6 x 10(-7) M-1 20:4(n-6) and 22:6(n-3) for albumin; 3.9 and 14.6 x 10(-7) M-1 20:4(n-6) and 22:6(n-3) for AFP) with respect to the k'a calculated at 37 degrees C. Hence, k'a values were higher for albumin and lower for AFP than the corresponding values at 37 degrees C. It was concluded that uptake by cells and interaction of fatty acids with cell membranes depend mainly on the k'a of fatty acids and carrier proteins at equilibrium.

An attempt is made in this review to summarize new findings that propose the direct involvement of two fetal proteins (i.e, fetuin and alpha-fetoprotein) in fatty acid transport and delivery to cells. The presence of these proteins at a high plasma concentration in fetal life and the critical need for fatty acids during development strongly support this hypothesis. Tissue and cell specificities involved in the uptake of these fetal proteins and the mechanism of fatty acid delivery awaits further research.

Human mammary medullary carcinoma cells (passages 16 to 21) were cultured for 2 days to allow for attachment, followed by 6 days of culture in either fetal calf serum, human cord blood, human amniotic fluid, or growth factors in the presence or absence of purified human alpha-fetoprotein (AFP). When growth factors were tested alone, only platelet-derived growth factor produced a significant increase in cell proliferation. Although up to 40% amniotic fluid had no effect on cell proliferation, human cord blood was two-fold more potent than fetal calf serum at similar concentrations. The addition of 10 ng/ml of platelet-derived growth factor increased the proliferative activity of human cord blood 1.5- to 2.5-fold. Ablation of endogenous AFP by affinity chromatography reduced the proliferative activity of cord blood by 75%. Similarly, the mitogenic activity of cord blood plus platelet-derived growth factor was reduced by 56% when AFP was removed. Purified AFP dose-dependently enhanced the proliferative activity of platelet-derived growth factor. This synergistic effect was specific for platelet-derived growth factor. We conclude that platelet-derived growth factor is a major growth factor controlling the proliferation of these tumor cells and that AFP may enhance growth factor proliferative activity and human mammary tumor growth.

Alpha-Fetoprotein (AFP) is a product of specific fetal tissues and of neoplastic cells of hepatocyte or germ cell origin in adults. This protein belongs to a gene family that is phylogenetically most closely related to serum albumin. Its primary, secondary, and tertiary structural aspects appear similar to the three-domain concept proposed for the latter protein. The primary sequence of AFP departs most widely from serum albumin in the first 135 amino acid residues, with about 42% of the remaining 590 residues of the human proteins being identical. Some evidence exists that there are limited sequence differences in the AFP of a given animal species. AFP shows considerable charge heterogeneity that appears to relate mostly to its glycoid moiety. The proteins of some species such as the rat show more pronounced heterogeneities than that of humans. The variations in extent and type of glycosylations are evidenced by differences in the binding to various lectins. These interactions are being extensively explored in attempts to differentiate the sources of the protein produced by various normal and neoplastic cells and may provide valuable diagnostic methods. AFP, like serum albumin, shows relatively strong binding affinities for a variety of ligands. The most notable difference is the strong preferential binding of polyunsaturated fatty acids by AFP. This protein may play a role in transporting these substances to developing and to malignant cells. Various agents affect the synthesis of this protein both by specific fetal tissues and by neoplastic cells. Marked differences in the responses of cells, particularly those of neoplastic types, are indicative of variations in the genetic factors responsible for control of its synthesis. The subject of the genomic repression of the synthesis of AFP seen in fetal life upon maturation of the liver and the reoccurrence of synthesis upon malignant conversion of hepatocytes and of certain germ cells are of particular interest. The regulation of the closely related AFP and albumin genes is providing a powerful and attractive model to examine molecular events in the activation and inactivation of specific genes during development and in oncogenic processes. Extensive measurements of AFP during pregnancy and in the course of neoplasias, notably hepatoma, are being made to aid in following changes in such developments. Various specific physiological roles for this protein are also being proposed. One of these is its possible action in the regulation of immune processes.(ABSTRACT TRUNCATED AT 400 WORDS)

Crude Pedersen fetuin, derived from fetal bovine serum, contains adipogenic activity. Biochemical characterization was undertaken by following the differentiation of the 1246 adipogenic cell line. The present paper provides evidence that crude fetuin contains distinct proteins with adipogenic activity. By molecular sieve fractionation using Sephacryl S-300, the majority of adipogenic activity eluted in two distinct peaks, FI (molecular weight greater than 669 kDa) and FII (molecular weight ranging from 445 and 232 kDa). In addition a minor activity was found in a third peak, FIII (molecular weight around 69 kDa). Partial purification and biochemical characterization indicate that FI and FII are two distinct factors. FI has a PI higher than 9.4, is destroyed by alkaline treatment, and is stable when treated with acid. FII has a PI lower than 4.0, is alkali stable, but is destroyed completely by treatment with acid. Moreover, our data show that adipogenic factors are distinct from another protein alpha 2 macroglobulin known to be found in crude Pedersen fetuin. These results suggest that serum contains two large molecular weight proteins bearing adipogenic activity which could play an important role in the control of the adipose differentiation process.

While using transgenic mice to study the regulation of alpha-fetoprotein (AFP) it was noted that two different alpha-fetoprotein-chloramphenicol acetyl transferase (CAT) transgenes resulted in the appearance of craniofacial anomalies in 11% of the offspring derived from crosses between transgenic mice and nontransgenic mates. A total of 13 fetuses exhibited abnormalities; two are described in detail. Ninety-two percent of the affected fetuses had some form of mandibular abnormality while zygomatic and ossicular defects appeared in more than 40% of the specimens. Aglossia and aberrant musculature were also present in the most severely involved specimen. Eight of the affected fetuses were screened for the presence of the AFP-CAT plasmid and all were found to be heterozygous for the transgene. Since the probability that all 8 of the abnormal fetuses known to carry the CAT gene would have done so by chance was only 1 in 256, it may be assumed that these anomalies did not appear spontaneously, but were somehow created by the transgenic procedure. It is not known how the transgenic material led to the observed dysmorphogenetic pattern, but theoretically introduction of the AFP-CAT plasmid could have disrupted morphogenesis through the presence of the "foreign" CAT protein or a decrease in the availability of AFP. Since AFP levels were found to be normal in both the liver and the yolk sac of transgenic fetuses, it appears that the presence of CAT was responsible for the craniofacial anomalies described here.

Despite all the information about AFP presented, a great deal still needs to be discovered especially in pregnancy. Geographical and racial differences remain to be elucidated. Similarly, differences in obstetric population in Helsinki and Baltimore, for example, are only now being studied. Sex differences may exist; Lardinois and associates195 cited a higher level of AFP in male than female fetuses. The important questions that need to be answered are whether AFP assays can help improve the other half of prenatal care- that directed to the fetus- and whether the AFP model can help enhance our understanding of the similarities and differences of fetal and cancer cells.

An alpha-feto-protein (AFP) is present in many mammals, in birds, and in sharks during development. The AFP present in different species have similar physicochemical properties and often have common antigenic determinants. Their study, both in health and disease, has provided a useful model for the understanding of other phase-specific antigens and the activation of the genes which control their synthesis. In the human fetus, the level of AFP falls with increasing maturity. The more sensitive methods of detection have disclosed that this fetal protein persists in trace amounts throughout life and its level increases in maternal blood during pregnancy. The principal sites of synthesis are the fetal liver and in some mammals, the yolk sac splanchnopleur. In humans as well as in mice and cows, it is notable that the synthesis of AFP is increased in liver cancer cells and that high levels of this protein are present in serum. Elevated values of AFP have also been detected in human subjects with undifferentiated tumours of the testis and ovary. A fall to normal levels has been noted in cases of complete remission after surgery and a return to high levels in patients who develop metastases. In some patients with hepatitis a temporary rise in the level of AFP has also been observed. In recent years, the detection of high levels of AFP in amniotic fluid has proved to be of great value for the prenatal diagnosis of neural-tube defects. Abnormal levels have also been found in the amniotic fluid or in maternal serum in cases of spontaneous abortion. Such measurements are now being assessed as a methodof monitoring abnormal pregnancy.

The influence was studied of BaSO4 (i.p.) pretreatment on the mediator induced inflammatory responses: oedema formation, measured plethysmographically, increased vascular permeability to protein, measured by the extravascular accumulation of 125I-labeled albumin (125I-HSA) and vasodilatation, measured by the accumulation of 51Cr-labeled erythrocytes. Subplantar application of histamine, 5-hydroxytryptamine, bradykinin or prostaglandin E2 caused oedema formation, an enormous 125I-HSA accumulation and a relatively small 51Cr-labeled erythrocytes accumulation. BaSO4 pretreatment inhibited all these inflammatory responses to a high extent, while the alpha M-foetoprotein (alpha MFP) serum levels were increased from a normal value of 188 +/- 123 micrograms/ml up to 5200 +/- 2264 micrograms/ml (n = 29). From this study and previous data using purified alpha MFP it could be assumed that the anti-inflammatory effects induced by BaSO4 pretreatment are mediated by this enormous increase of the alpha MFP serum levels of alpha MFP are nonspecific and possibly caused by a coating and/or membrane stabilizing effect on cell membranes and/or endothelial junctions.

The DNA sequences of the 14 exon junctions in the murine alpha-fetoprotein gene were determined using cloned genomic DNA. When these exons were examined with respect to the polypeptide segments they encoded, a direct correspondence between a threefold repeat of four exons and three protein domains was observed. Nucleotide sequence comparisons among the four exons of each domain were used to deduce the likely structure of the primordial domain, and the order and mechanism of its triplication to form the tripartite ancestral gene from which both alpha-fetoprotein and serum albumin arose. Sequence homologies among the four exons that constitute a single domain also suggest that they were derived, at least in part, from a common sequence which underwent successive amplification and divergence.

In rats bearing Morris hepatoma No. 7777, serum levels of alpha fetoprotein (AFP) increased as tumour size increased. Hepatoma-bearing females remained in dioestrus once the tumour exceeded a cross-sectional area of 12 cm2. The following changes were seen in tumour-bearing rats compared to control animals: uterine wet weight was significantly decreased, the uterine epithelial mucosa was lower, castration cells developed in the anterior pituitary, and there was a 3- to 23-fold elevation in serum oestrogen levels. We conclude that circulating oestrogen is bound to AFP in hepatoma-bearing female rats and that in this bound state it is unable to exert its normal physiological actions.

During chemical hepatocarcinogenesis by N-2 fluorenylacetamide in adult female Rats, vaginal cycle alterations were observed after 30 days of carcinogenic diet, and a blocking at the metestrus stage appeared from the 70th day. This may be explained by the very low serum progesterone level prevailing after the 50th day. An important drop in ovary weight was also noticed; together with the blocking of follicular maturation and ovulation leading to a marked follicular atresia. Simultaneously, alpha-fetoprotein (AFP) seems to interact in the lowering of progesterone level, and AFP was found ten times higher in the serum of treated animals than in controls. AFP was localized in degenerative oocyte cytoplasm by immunofluorescence in the treated animals, but not in the controls. In conclusion, a blocking role of AFP on genital cycles and a relationship between AFP and follicular atresia are suggested.

Alpha-fetoprotein (AFP) is the dominant serum glycoprotein of fetal life but is expressed only in low nanogram levels in adult sera. A possible explanation for this is that AFP has immunoregulatory properties which may be essential during early ontogeny but unnecessary, if not harmful, in adulthood. The current study shows that the interleukin 2 (IL-2)-dependent division of Lyt 2- T blast cells previously activated in autologous mixed lymphocyte reactions (AMLR) or by stimulation with concanavalin A (Con A) is susceptible to inhibition by AFP. This anti-proliferative activity appears to be independent of any competitive interaction with either IL-2 or I-A antigens and is therefore likely to result from a direct action of AFP on the T cells. These findings support the hypothesis that naturally occurring elevated levels of AFP may be involved in the protection of the conceptus from potentially harmful maternal anti-fetal reactivity and in the establishment and maintenance of T-helper cell tolerance to antigens encountered during early life.

Theories to explain the failure of rejection of the fetus by the mother during pregnancy include immunologic privilege of the uterus as a graft site, lack of transplantation antigen expression on the trophoblast, weakening of maternal cellular immunity during pregnancy, and separation of maternal and fetal circulations. Evidence for and against each of these theories is discussed. Local concentration of a variety of hormones, including human chorionic gonadotropin (HCG), sex steroids, alpha-fetoprotein, and immunoglobulins, could provide a blocking mechanism to prevent maternal cellular immune attack. Possibly, progesterone, antibodies, and immune complexes are important in protecting the placenta and ultimately the fetus from rejection. Elucidation of regulatory mechanisms in pregnancy may be applicable to other problems in immunology.

The biologic and clinical significance of the oncofetal antigens carcinoembryonic antigen (CEA) and alpha1-fetoprotein (AFP) are discussed. Although the current assays for these molecules are not tumor-specific, measurement of these molecules in the circulation of cancer patients is useful either for tumor diagnosis or for management of the cancer patient in the postoperative or post-chemotherapy state. An approach to increasing the specificity of the CEA radioimmunoassay is described.

Neonatal male and female mice, ages 1-5 days, were injected intracranially with either anti-alpha-fetoprotein (AFP) IgG, steroids, or various control solutions. The mice were autopsied 60-70 days later and the spleen, thymus, liver and gonads were examined by light microscopy. The antibody to AFP produced a gonadal response which was sexual specific. Histological examination of the tissue sections from female mice treated with either anti-AFP IgG or steroids revealed the presence of polyfollicular ovaries lacking in corpora lutea formation. A comparable antibody-induced specific effect on the testes could not be demonstrated; however, steroidal administration induced aspermatogenesis and delayed maturation in parallel studies. In the anti-AFP IgG-treated groups, there appeared a gross neurological lesion which was termed external hydrocephaly. The physiologic responses in the female gonad were found independent of the presence of this anatomical brain lesion, whereas those in the male gonad were found causally related. The immunological specificity of the gonadal response was demonstrated by the use of IgG devoid of anti-AFP IgG and by various IgG control solutions. Thus, exposure to anti-AFP IgG during the critical period of sexual development in the brain appears to mimic steroidal androgenization of the female mouse.

Some rat strains permanently accept allogenic livers without pharmacological immune suppression. In the same donor/recipient combinations, other organs as heart, kidney or skin are normally rejected. The transplanted liver not only withstands its own rejection, but also induce donor-specific immune tolerance. The mechanisms responsible for this effect may be clonal deletion, activation of suppressor cells or immune suppressive circulating factors as anti-class II-antibodies. An "immune-privilege" of an orthotopically transplanted liver exists also in pigs and, however to a lesser extent, in other large mammalian species including man. Regeneration of liver tissue altered by the transplantation procedure may produce the signals for induction of tolerogenic mechanisms.

Sexual differentiation of reproductive and behavior patterns is largely effected by hormones produced by the gonads. In many higher vertebrates, an integral part of this process is the induction of permanent and essentially irreversible sex differences in central nervous function, in response to gonadal hormones secreted early in development.

The application of nucleic acid hybridization techniques to the study of liver regeneration has led to a revision of some well-established ideas about the patterns of gene expression during regenerative growth. This paper focuses on two broad problems: a) the extent to which mRNA populations in regenerating liver differ qualitatively or quantitatively from those of normal liver, and b) the similarities and differences between the pattern of gene expression during liver regeneration and liver development. Answers to these questions have come from studies in normal and regenerating liver of, a) the proportion of non-repetitive and repetitive DNA transcribed, b) the complexity of mRNA populations and the abundance of sequences in these populations, c) the extent of homology between mRNA populations, d) the amounts of specific mRNAs for albumin, alphafetoprotein, and fibrinogen, and e) the transcription of some cellular oncogenes. Changes in the abundance of liver mRNA transcripts, without major qualitative alterations in the spectrum of sequences contained in the RNA populations, are sufficient to permit the transition of hepatocytes from a resting into a dividing state. Transcripts from at least two cellular oncogenes are included among the mRNA sequences which become more abundant during liver regeneration. Analysis of the expression of some specific genes (albumin, alphafetoprotein and fibrinogen) during liver regeneration suggests that there is little similarity between the patterns of gene expression in regenerating and developing liver.

Several purified glycoproteins including laminin, fetuin, and human chorionic gonadotropin promote dose-dependent and saturable adhesion of Mycoplasma pneumoniae when adsorbed on plastic. Adhesion to the proteins is energy dependent as no attachment occurs in media without glucose. Adhesion to all of the proteins requires sialic acid, and only those proteins with alpha 2-3-linked sialic acid are active. The alpha-subunit of human chorionic gonadotropin also promotes attachment, suggesting that a simple biantennary asparagine-linked oligosaccharide is sufficient for binding. Soluble laminin, asparagine-linked sialyloligosaccharides from fetuin, and 3'-sialyllactose but not 6'-sialyllactose inhibit attachment of M. pneumoniae to laminin. M. pneumoniae also bind to sulfatide adsorbed on plastic. Dextran sulfate, which inhibits M. pneumoniae binding to sulfatide, does not inhibit attachment on laminin, and 3'-sialyllactose does not inhibit binding to sulfatide, suggesting that two distinct receptor specificities mediate binding to these two carbohydrate receptors. Both 3'-sialyllactose and dextran sulfate partially inhibit M. pneumoniae adhesion to a human colon adenocarcinoma cell line (WiDr) at concentrations that completely inhibit binding to laminin or sulfatide, respectively, and in combination they inhibit binding of M. pneumoniae to these cells by 90%. Thus, both receptor specificities contribute to M. pneumoniae adhesion to cultured human cells.

The mechanisms by which lymphoid cells produce infinitely variable molecules of the immunoglobulin protein superfamily have been recently elucidated. These molecules serve, in part, as the mediators of cell:cell recognition and interaction among lymphoid cells. However, the generality of those molecular mechanisms to occur in non-lymphoid cell types has not yet been established. In this paper, we propose that the serum albumin superfamily of proteins has the necessary characteristics to serve analogous functions in epithelioid cells, and we critique recent evidence which leads to this hypothesis.

Serum gamma-glutamyl transpeptidase from patients with various hepatobiliary diseases was fractionated by polyacrylamide gradient gel slab electrophoresis to study the specific patterns of gamma-glutamyl transpeptidase fractions in hepatic cancer. On zymograms of normal serum gamma-glutamyl transpeptidase, a total of 10 fractions was observed. Additionally, fractions I', I" and II' were recognized in sera from hepatocellular carcinoma patients. Among these, fraction I', which migrated slightly, but significantly, slower than fraction I was the most specific; it was found in 55% of the hepatocellular carcinoma patients. Fractions I" and II' were also relatively specific, each was observed in about 29% of these patients. Fractions V to IX were observed in few hepatocellular carcinoma cases. Fraction I' is thought to be a hepatoma-related fraction, highly specific for the serum of hepatocellular carcinoma patients. Fractions I" and II' were also thought to be hepatoma-related fractions of gamma-glutamyl transpeptidase. We suggest that fractions I', I" and II' may be useful in the diagnosis of hepatocellular carcinoma.

The development of new analytic and preparative techniques in the field of protein chemistry has essentially extended our knowledge about the variety of human plasma proteins in the last 15 years. In many cases plasma proteins have been particularly determined by immunologic techniques, partially highly purified and physicochemically well characterized, before knowing the biological function. To these proteins belong among others the alpha 1-antitrypsin, Cl-inactivator, alpha 2-macroglobulin, Gc-globulin and the cold-insoluble globulin. Today we know more than 100 proteins being isolated from human plasma and among these are nearly 20, of which the biological function is not yet known. To this group are belonging proteins, which are known since many years, like the alpha 1-acid glycoprotein and the C-reactive proteins as well as proteins, which have only been described in the last years and which partially have an interesting chemical structure, e.g. the histidinerich 3,8S-alpha 2-glycoprotein and the leucine-rich 3,1S-alpha 2-glycoprotein, of which every fifth amino acid is formed by leucine. It is to be hoped that the special chemical structure of some of these human plasma proteins as well as the quantitative immunologic determination in different patient sera will give hints to their biological function.