Tissue specificity of alpha-fetoprotein messenger RNA expression during mouse embryogenesis

Alpha-fetoprotein (AFP) is a synthetic product of only the visceral yolk sac endoderm and fetal liver during mouse embryogenesis. To examine the involvement of transcriptional and post-transcriptional mechanisms in the regulation of tissue-specific expression of the AFP gene, the distribution of AFP mRNA in tissues at different stages of development was determined. Total RNA was isolated from mid-gestation tissues, and a microextraction procedure was developed for earlier stage embryos where the amount of tissue was limited. AFP mRNA was measured by a dot-hybridization assay using a 32P-labelled AFP cDNA clone as probe. Results show that only visceral yolk sac endoderm and fetal liver of midgestation embryos contained AFP mRNA. At earlier stages AFP mRNA was confined to regions within the visceral endoderm which have previously been shown to be AFP positive. These results indicate that expression of the AFP gene during post-implantation development is probably controlled at the level of AFP gene transcription. In addition, we show by in situ hybridization to tissue sections that all endoderm cells of the visceral yolk sac contain AFP mRNA, indicating that the visceral endoderm layer is a homogeneous population of cells with respect to transcription of the AFP gene.

Identification and partial characterization of a lactogen from the midpregnant mouse conceptus

Previously, we demonstrated that measurement of serum lactogenic hormones during pregnancy in the mouse by the rabbit mammary gland radioreceptor assay (RRA) and specific RIAs for mouse PRL (mPRL) and mouse placental lactogen (mPL) showed a large RRA to RIA activity ratio during midpregnancy. The purpose of this study was to begin to characterize this discrepancy in midpregnancy PRL-like activity. The elution profile of serum from midpregnant mice on Sephadex G-100 showed a characteristic peak in RRA activity (elution volume/void volume = 1.5), distinct from either mPRL or mPL (both approximately elution volume/void volume = 2.0). This PRL-like activity was not recognized by antisera to either mPRL or mPL. The source of the midpregnancy lactogen was localized to the conceptus. The hormone was found to have an apparent molecular weight of 50,000 (based on Sephadex G-100 chromatography) and an electrophoretic mobility similar to mPRL (Rf = 0.5-0.6) and to be lactogenic in the in vitro mouse mammary gland explant bioassay. We have demonstrated the existence of a midpregnancy lactogen that is different from mPL and mPRL and is of conceptus origin.

Differential expression of lectin receptors in germ layers of the mouse egg cylinder and teratocarcinomas

Receptors for three lectins with restricted specificities, namely fucose-binding protein of Lotus tetragonolobus (FBP), peanut agglutinin (PNA) and Dolichos biflorus agglutinin (DBA), were distinctively located in 6- and 7-day mouse embryos and in embryoid bodies of teratocarcinoma OTT6050 grown in vivo. Thus, FBP reacted mainly with the inner cells (embryonic ectoderm and teratocarcinoma stem cells), DBA reacted with the outer cells (endoderm) and PNA reacted with all the germ layers including mesoderm. Upon in vitro culture of the embryoid bodies, the exposed stem cells express DBA receptors. Since the receptors for the three lectins in teratocarcinomas are known to be carried by the large carbohydrate chains characteristic of early embryonic cells, the present result suggests that terminal structure of the large carbohydrates is altered according to the direction of the differentiation or to the position of the cells in embryos and in teratocarcinomas.

S100 protein in human chordoma and human and rabbit notochord

S100 protein is a protein that has been considered to be specific for tissues of neuroectodermal origin; however, recent studies have demonstrated the presence of S100 protein in mesodermal tissues. Using immunohistochemical methods, we found S100 protein in human chordomas and in human and rabbit notochordal tissue. Our findings suggest that S100 protein is present not only in neuroectodermal tissue but in mesodermal tissue, which develops in close proximity to neuroectoderm.

5-methylcytosine content in different organs of the mouse and rat, several tumors and in mice embryos

1. The content of 5-methylcytosine of the DNA of 11-day old mice embryos was compared with that of the DNA of different plasmocytoms. 2. Furthermore the DNA content was determined in different transplantable tumors and normal organs of the rat and the mouse. 3. By the aid of liquid chromatography significant differences could be demonstrated in the content of 5-methylcytosine of the DNA of BALB/c-mice or NMRI-mice and the DNA of the plasmocytom MOPC 104 E and MOPC 141, but not in the case of MOPC 321. 4. Clear differences could be observed with restriction enzymes: the DNA of all the plasmocytoms studied is more digested with Hpa II and Hha I than the DNA of the embryos. This is not the case however with MSP I. 5. The DNA of three transplantable tumors tested contains less 5-methylcytosine than the one of the liver kidney of the mouse and the rat. This was confirmed with restriction enzymes too.

Localization of receptors for Dolichos biflorus agglutinin in early post implantation embryos in mice

The distribution of receptors for Dolichos biflorus agglutinin (DBA) was studied by histochemical staining of paraffin sections with HRP- or FITC-DBA in mouse embryos at stages ranging from 4.5 to 12.5 days post coitum. Preimplantation blastocysts did not express DBA receptors. The receptors first appeared in primitive endoderm cells in 5-day embryos. In 5.5- to 7.5-day embryos, both the parietal and extraembryonic visceral endoderm cells expressed the receptors. Reichert's membrane was negative for DBA receptors. The columnar cells of the embryonic visceral endoderm (EVE) strongly expressed the receptors, while the flat cells at the antimesometrial pole of the EVE were negative or patchily positive. In 8- to 9-day embryos, the receptors were expressed in the epithelium of the fore- and hindgut. In 9.5- to 12.5-day embryos, the epithelial cells of various regions of the gut expressed the receptors, although the endodermal cells of the liver and the pancreas, both derived from the foregut, did not express them. In 8- to 12.5-day embryos both the visceral and parietal yolk sac endoderm were positive in DBA receptors. The receptors were localized exclusively on the free surface facing the yolk cavity or on the luminal surface and subjacent cytoplasm. All endodermal cells which were positive are known to have absorptive activity. All other tissues in these stages were negative in DBA receptors.

Cultivation of mouse embryos explanted at 11 days

A method for cultivation of 11-day mouse embryos (plug day = day 0) is presented. Competence of the visceral yolk sac and serum dilutions were tested. Eleven day mouse embryos were cultivated for 24 hours with the visceral yolk sac either opened or left intact. Fetal calf serum (FCS) at 0%, 25%, and 50% dilutions balanced with Waymouth's medium was used as cultivation medium. Viability and growth of the embryos were evaluated by heart rate at 6 hours, and protein accumulation and differentiation at 24 hours. At 6 hours, best results were found in those embryos with the visceral yolk sac intact. Serum dilutions at this time were not important for viability. At 24 hours, only those embryos cultivated with the visceral yolk sac opened were alive. Significant increase in viability was obtained when a 50% dilution of FCS was used. There was a significant increase in protein accumulation for viable embryos at 24 hours.

Culture of 91/2-day rat embryos in human serum supplemented and unsupplemented with rat serum

We attempted to grow explanted 91/2-day rat embryos in vitro in human serum but were unable to demonstrate normal growth as has been previously described. The embryos were consistently smaller, anaemic, and frequently deformed. These abnormalities were overcome by supplementing the human serum with 10% rat serum. The latter possibly provides yet unidentified essential growth factors required by rat embryos that are not present in human serum.

Kinetic study of fatty acid composition of day 7 to day 14 cow embryos

Day 7 to Day 14 cow embryos were analyzed by gas chromatography and mass spectrometry for their fatty acid content. The total amount per embryo does not change between Day 7 and Day 10, but then increases sharply between Days 11 and 13, suggesting that it is related to blastocyst volume or weight. With increasing embryonic age, there is an increase in the fatty acid elongation and desaturation. Arachidonic acid is present in significant amounts on Day 14 which may indicate that prostaglandin synthesis has started. The composition of the fatty acids bound to bovine serum albumin (BSA) is similar to that for embryos. Therefore, this macromolecule may be of special value for adding lipids in culture media for mammalian embryos.

Decreased ornithine decarboxylase in the fetal hydantoin syndrome

The anticonvulsant diphenylhydantion (DPH) causes embryonic folate antagonism in the animal model of the fetal hydantoin syndrome. Thus, comparisons were made between the metabolic effects of the teratogens DPH and 9-methyl pteroylglutamic acid (9-methyl PGA), a folate antagonist. The DPH inhibited ornithine decarboxylase (ODC), the rate-limiting enzyme in putrescine biosynthesis, and caused reduced levels of this precursor diamine as well as the resultant polyamines, spermidine and spermine. In contrast, embryos from rats treated with 9-methyl PGA had ODC activity similar to controls and increased levels of putrescine, spermidine, and spermine. Because ODC is an enzyme of major importance for embryogenesis, any alterations in ODC activity may indicate abnormal development.

Mouse embryonic transforming growth factors related to those isolated from tumor cells

Growth factors with the two characteristic properties of sarcoma growth factor, the ability to stimulate anchorage-independent growth of normal mouse or rat fibroblasts and the ability to compete with 125I-labeled epidermal growth factor for receptor binding, can be isolated from 12- to 13-day-old normal mouse embryos of various strains. Two size classes of the transforming factor from embryo cells can be isolated with apparent molecular weights of 20,000 and 10,000. The lower-molecular-weight factor has been purified several hundred-fold and has the same properties as the peptides with a molecular weight of 10,000 produced by mouse sarcoma virus-transformed 3T3 cells. Whole-mouse embryos contain approximately 10% as much sarcoma growth factor per g of tissue as do the murine sarcoma virus-transformed cells; how it is distributed among the embryonic tissues remains to be determined.

Immunohistochemical characterization of renin-containing cells in the human juxtaglomerular apparatus during embryonal and fetal development

Thirty kidneys from nine embryos, 20 fetuses, and one full-term baby were examined for their renin content by immunofluorescence and the peroxidase antiperoxidase method, using an antihuman renin antiserum. Renin-containing cells were found in the early metanephros (5-week-old fetuses). Most of them were located in the wall of well-developed renal arteries in the vicinity of the prospective vascular pole of the glomeruli. In the poorly differentiated peripheral renal cortex, intracellular fluorescence was seen in nearby arterioles of pocket-like s-shaped tubules. Rarely, labeled cells were found in the wall of major branches of renal arteries. In all locations, the renin-containing cells appear to be clearly linked to the development of the renal vascular system.

Indomethacin--placental transfer, cytotoxicity, and teratology in the rat

Aspirin is a well-known teratogen in laboratory animals and is an inhibitor of prostaglandin synthesis. To further investigate the inhibition of prostaglandin synthesis as a mechanism of teratogenesis, we examined the teratologic potential, cytotoxic potential, and placental transfer of indomethacin in the rat. Indomethacin was not teratologic, not cytotoxic to cells in the embryonic hindlimb bud, and did not cross the placenta in physiologically significant amounts on days 11 to 12 of gestation. Near parturition, however, indomethacin crossed the placenta in pharmacologically significant amounts. The pharmacokinetics of placental drug transfer are discussed.

[Animal analogs of human embryonal prealbumin-2]

Immunochemical analogs of human embryonal prealbumin-2 (EPA-2) were found in blood sera and amniotic fluid of the cow, sheep and pig fetuses. Meanwhile they were not detected in blood sera of adult animals. Analogs of animal EPA-2 produced the reaction of complete immunochemical identity with human EPA-2. Moreover, they have similar physicochemical properties and electrophoretic mobility of prealbumins. The indirect immunofluorescence technique was used to locate EPA-2 in collagenic fibres of fetuses and in adult animals' connective tissue. It is suggested that EPA-2 might be the protein contained by procollagen or by non-collagenic components of collagenic fibres.

[Animal analog of human embryonal prealbumin-1 (EPA-1)]

Immunochemical analogs of human embryonal prealbumin-1 (EPA-1) were found in the cow, sheep and pig. They produced the reaction of inhibition of the precipitation line in the standard EPA-1 test-system. However, the analogs of EPA-1 in the cow, pig and sheep as compared to each other produced the reaction of complete immunochemical identity.

[Normal 17-day human embryo. Qualitative and quantitative characteristics of protein components]

Protein components in the definitive and provisory anlages of the 17-day-old human embryo "Krym" have been studied in a complex investigation. Acidic, basic and summary proteins, nucleoproteids and some amino acids (histidine, arginine and lysine) have been analysed. Quantitative estimation of histones, histone-like and common proteins has been performed by means of the probe spectrophotometer in corresponding wave lengths at the probe size of 1 mkm. It has been demonstrated that in zones of intensified cell proliferation and differentiation contents of the histone-like proteins and nucleoproteids are increased. These zones are presented in the germ shield by the prechordal plate. Hensen's nod and primary streak, and in the chorionic membrane--by the trophoblastic integument and by the wall of the forming blood vessels. Certain asynchronity in differentiation of chorionic villi of various morphological types is also noted, it is one of the most important ontogenetic regularities in the formation of morpho-functional correlations in the system mother-fetus.

Structural components and characteristics of Reichert's membrane, an extra-embryonic basement membrane

This paper presents an analysis of mouse and rat Reichert's membrane, a thick basement membrane formed between the trophoblast and parietal endoderm cells of early mammalian embryos. When analyzed by polyacrylamide gel electrophoresis. Reichert's membranes from rat and mouse conceptuses appear simple and consist primarily of collagen and 4 noncollagenous glycoproteins of approximate Mr = 415,000, 245,000, 170,000, and 50,000. The proteins at 415,000 and 245,000 are similar in molecular weight to laminin and are immunoprecipitated by anti-laminin antiserum. The protein at 170,000 is co-precipitated with laminin and represents a novel form of a laminin-like protein, whereas the protein at 50,000 is unrelated to laminin. Using metabolic labeling experiments, it is shown that parietal endoderm cells synthesize these components and incorporate them into the matrix in organ cultures but do not degrade Reichert's membrane in the conditions used over a 6-day culture period. Evidence is presented that the high molecular weight collagenase-sensitive proteins (greater than 420,000) observed on polyacrylamide gel electrophoresis are due to lysyl oxidase-derived cross-links between Reichert's membrane components.