Regulation of Fibroblast Functions by Products of Schistosomal Egg Granulomas: Potential Role in the Pathogenesis of Hepatic Fibrosis

Recent observations suggest a molecular link between granuloma formation and hepatic fibrosis in schistosomiasis. Egg granulomas isolated from Schistosoma mansoni-infected mice, when cultured in serum-free medium, produce a variety of biologically active molecules that affect fibroblast function. One group of molecules--proteins with an estimated relative molecular mass (Mr) of 30 000--stimulate fibroblast proliferation in vitro. These molecules have interleukin (IL)-1-like activity when assayed in thymocyte cultures but are biochemically distinct from previously characterized murine IL-1. Fibroblast mitogenic activity is also produced by macrophages isolated from granulomas and by extracts of S. mansoni eggs. The egg-derived activity is distinct from the granuloma cell-derived material on the basis of Mr and isoelectric point determinations. Egg extracts also contain concanavalin A-binding substances which are not directly mitogenic for fibroblasts but can stimulate spleen cells from infected mice to produce fibroblast mitogenic activity in vitro. A large chemoattractant molecule (greater than 200 000 Mr) for fibroblasts has also been identified in supernatants from granuloma cultures and in supernatants from macrophages isolated from granulomas. This activity is abolished by treatment with anti-fibronectin antibody, suggesting that it is fibronectin or a cleavage product thereof. Molecules similar to or identical with the fibroblast mitogenic factors from the granulomas have been identified, and they inhibit the contraction of fibroblast-populated collagen lattices. These activities may be important in the pathogenesis of hepatic fibrosis in schistosomiasis, and pharmacological modification of their production or of their effects on target fibroblasts might theoretically prevent hepatic fibrosis in this disease.

Localization of oviductal glycoproteins within the zona pellucida and perivitelline space of ovulated ova and early embryos in baboons (Papio anubis)

The estrogen-dominated baboon oviductal epithelium synthesizes and secretes a family of oviduct-specific glycoproteins. The objective of this study was to determine if these glycoproteins become associated with ova and early embryos. Ovarian and oviductal eggs obtained from superovulated baboons 72 h post-hCG were subjected to an indirect immunofluorescent assay that used a polyclonal antibody prepared toward the baboon oviduct-specific glycoproteins. Oviductal ova as well as 2-cell and 4-cell embryos showed intense, specific fluorescence within their zonae pellucidae. Ovarian ova did not exhibit fluorescence. Oviductal eggs were also fixed and processed for peroxidase-antiperoxidase immunocytochemistry and colloidal gold immunoelectron microscopy to confirm the immunofluorescent data and to determine the subcellular distribution of the antigens. Oviductal ova as well as 2-cell and 3-cell embryos exhibited immunolabeling localized within the zona. Gold particles were distributed uniformly throughout the width of the zona. Occasional groupings of gold particles were observed within the zona. Also, in most eggs, immunoreactivity was observed associated with flocculent material in the perivitelline space as well as the vitelline membrane. Furthermore, immunogold labeling above background level was noted in the cytoplasm of the eggs, particularly in the blastomeres of 3-cell embryos. Collectively, these results indicate that baboon estrogen-dependent oviductal secretory glycoproteins become intimately associated with oviductal ova and with embryos.

Isolation, characterization, and immunochemical properties of a giant protein from sea urchin egg cytomatrix

A giant protein of apparent molecular weight (Mr) 2000 kDa, as determined by SDS-PAGE, was isolated and partially purified, under denaturing conditions, from the detergent-resistant cytomatrix of unfertilized sea urchin egg. Immunoblot analysis and indirect immunofluorescence microscopy observations indicated that this high-molecular-weight protein cross-reacted with the immunospecific serum raised against chicken breast muscle beta-connectin. However, rotary-shadowing electron microscopy images of the protein revealed short threadlike structures which appear morphologically different from beta-connectin structure. Indirect immunofluorescence localization of the protein with anti-beta-connectin serum showed a distribution throughout the whole unfertilized egg cytomatrix. This immunofluorescence pattern seems to change upon egg fertilization, since at metaphase the fluorescence stain appears to be excluded from the mitotic apparatus region as revealed by the double immunolabeling with anti-beta-connectin serum and monoclonal anti-alpha-tubulin antibody. Moreover, when egg cortical fragments were double-labeled with anti-beta-connectin serum and rhodamin-conjugated phalloidin, it was observed that the microfilaments assembled after fertilization seem to be in close association with the protein at the cleavage furrow and other locations. The possible significance of this sea urchin egg connectin(titin)-like protein is discussed.

Isolation and properties of a soluble fraction of Paracentrotus lividus sea urchin eggs responsible for the calcium-induced oxidative burst

The system responsible for the oxidative burst (OB) activity in Paracentrotus lividus eggs is different from those described earlier for other sea urchin species. The OB in P. lividus is associated with a soluble fraction resulting from centrifugation at 150,000 g. A low-molecular-weight, -SH-containing molecule present in this supernatant is required for the OB activity. The sulfhydryl reagent N-ethylmaleimide completely inhibits the calcium stimulated OB activity of intact eggs in the presence of the calcium ionophore A23187, suggesting that this requirement of low-molecular-weight -SH-containing molecules for OB exists also in vivo.

Development of cortical vesicles in Sicyonia ingentis ova: their heterogeneity and role in elaboration of the hatching envelope

In the marine shrimp Sicyonia ingentis, ova lack cortical vesicles at spawning. Previous ultrastructural studies suggested that two different populations of cortical vesicles (dense vesicles and the ring vesicles) appear within 30 min post-spawning. These vesicles undergo sequential exocytosis (exocytosis of the dense vesicles followed by exocytosis of the ring vesicles) that leads to the formation of a hatching envelope around the ovum (see Pillai and Clark: Tissue & Cell 20:941-52, 1988). In the present study, lectins were used as molecular probes to study the development of cortical vesicles subsequent to spawning and the role of these vesicles in formation and elaboration of the hatching envelope. Isolated envelopes were screened with 11 different lectins to determine what group(s) were specific to the envelope glycoconjugates; Concanavalin A (Con A), Griffonia simplicifolia (GS II), Lens culinaris (LCA), and wheat germ agglutinin (WGA) bound to the envelopes. FITC-lectin studies of sectioned ova (fixed at various time points after spawning) utilizing WGA and LCA showed different labelling patterns. Data obtained at the light microscopical level indicated that WGA was specific to the dense vesicles and the outer portion of the envelope, while LCA exhibited specificity for the ring vesicles and the inner portion of the envelope. At the ultrastructural level, gold-LCA labelling was seen associated with the cisternal elements (containing ring-shaped structures), ring vesicles, and the inner layer of the fully formed envelope. These data demonstrated that 1) the ring vesicles are formed by fusion of cisternal elements containing ring-shaped structures; 2) the two species of cortical vesicles are chemically heterogeneous; and 3) the components of each type of vesicle contribute to different integral parts (the outer and inner layers) of the hatching envelope.

Comparative studies of carbohydrate-binding proteins from Xenopus laevis skin and eggs. Sugar-binding specificities and affinity purification

Salt and detergent extracts of acetone-dried powder of Xenopus laevis skin and eggs were fractionated on sugar-Sepharose columns, to which lactose, melibiose, galactose, rhamnose and mannose had been covalently linked, by successive elution with chelating reagent and specific sugars, resulting in separation of the different Ca2(+)-dependent and Ca2(+)-independent carbohydrate-binding proteins. The skin of X. laevis contains a salt-extractable Ca2(+)-dependent lactose-binding lectin of 30 kilodalton (kDa) and the eggs a similar lectin of 43 kDa, but they both lack Ca2(+)-dependent galactose-binding lectins. The 30 kDa lactose-binding lectin which agglutinates human A erythrocytes was isolated by successive affinity chromatography on two linked sugar-Sepharose columns, i.e., a galactose-Sepharose-lactose-Sepharose (GL) column system. Since the 30 kDa lectin was not recovered in the Ca2(+)-dependent lactose-binding protein fraction from the GL column system under the dithiothreitol (DDT)-free conditions, it was concluded that the lectin requires the presence of DTT and calcium for binding to the lactose-Sepharose column.

The "lecithotrophic" sea urchin Heliocidaris erythrogramma lacks typical yolk platelets and yolk glycoproteins

The sea urchin Heliocidaris tuberculata undergoes typical development, forming an echinoid pluteus larva, whereas H. erythrogramma undergoes direct development via a highly modified, nonfeeding larva. Using a polyclonal antibody prepared against yolk glycoproteins from the typical developer Stronglyocentrotus purpuratus, we found that H. tuberculata contains cross-reactive proteins in abundance, but H. erythrogramma does not. In addition, we used immunoelectron microscopy to demonstrate that unfertilized eggs of H. tuberculata contain yolk platelets, but those of H. erythrogramma do not.

[The study of allergic children under one-year old. The measurement of IgE and IgG4 antibody titers to egg white, milk and soybean]

We measured the IgE and IgG4 antibody titers to egg white, and soybean of 94 allergic children under one year. (21 wheezy children, 35 atopic dermatitis, 34 wheezy children with atopic dermatitis, and 4 other allergic children). The results were as follows; 1) The positive ratio of IgE antibody titers to egg white was higher than the other IgE antibody titers, and of IgG4 antibody titers to milk was higher than the other IgG4 antibody titers. 2) Of each allergic symptoms, the positive ratio of IgG4 antibody titers to milk was higher than the others in wheezy children group. And the positive ratio of IgE antibody titers to egg white and milk were higher than the others in atopic children and wheezy children with atopic dermatitis. 3) The positive ratio of IgE antibody titers to egg white and milk were higher than the others in the group showed IgE RIST more than 21 IU/ml, and then the positive ratio of IgE antibody titers to egg white, milk and soybean and IgG4 antibody titers to egg white were higher than the others in the group showed eosinophil counts more than 301/mm3.

A new sialic acid analogue, 9-O-acetyl-deaminated neuraminic acid, and alpha -2,8-linked O-acetylated poly(N-glycolylneuraminyl) chains in a novel polysialoglycoprotein from salmon eggs

A new polysialoglycoprotein, designated PSGP(On), was isolated from the unfertilized eggs of the kokanee salmon, Oncorhynchus nerka adonis. 400-MHz 1H NMR analyses showed the O. nerka adonis PSGP contained alpha -2,8-linked oligo- and polysialic acid (polySia) chains that were made up of 4-O-Ac-, 7-O-Ac-, and 9-O-Ac esters of N-glycolylneuraminic acid (Neu5Gc) residues. The presence of a new sialic acid derivative, identified by 1H NMR as 9-O-acetyl-2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (trivial name, 9-O-acetyldeaminated neuraminic acid; 9-O-Ac-KDN), was also shown to be present as a minor component. The O-acetylated KDN residues appear to cap the nonreducing termini of the O-acetylated poly(Neu5Gc) chains. The O-acetylated polySia chains were resistant to depolymerization by bacterial exosialidases and a bacteriophage-derived endo-N-acylneuraminidase that is specific for catalyzing the hydrolysis of alpha -2,8-linkages in polySia containing either N-acetylneuraminic acid or Neu5Gc residues. After de-O-acetylation by mild alkali, the polySia chains were sensitive to digestion by endo-N-acylneuraminidase, yet partially resistant to exosialidase. These data confirm the alpha -2,8-ketosidic linkage in these chains and the nonreducing terminal location of the KDN residues. These results extend further the range of structural diversity in polySia-containing glycoconjugates, and in the family of naturally occurring sialic acids. They also suggest that the O-acetylated Neu5Gc and 9-O-Ac-KDN residues may have an important role during oogenesis.

Immunocytochemical evidence for centrosomal phosphoproteins in mitotic sea urchin eggs

The change in distribution of centrosomal phosphoproteins was examined in sea urchin eggs from fertilization to the first cleavage by immunofluorescence staining with the anti-phosphoprotein antibodies, MPM-1 and MPM-2. The antibodies reacted with female pronuclei in unfertilized eggs as well as centriolar complexes located at the base of sperm flagella. After insemination, male and female pronuclei fused together to form a zygotic nucleus which was visualized by staining of fertilized eggs with the antiphosphoprotein antibodies. No major change in staining pattern was detected in extracted whole eggs until mitosis. As the fertilized eggs approached mitosis, however, the antigens started to redistribute from nuclei to the perinuclear position where the mitotic centrosomes were located. Detailed immunofluorescence observation of isolated spindles revealed that the phosphoantigens were retained in isolated structures. A major 225 kd polypeptide was recognized by the antibodies, suggesting that the 225 kd protein is a phosphocomponent of centrosomes. The area recognized by the antibody in mitotic poles enlarged with the progress of mitosis, suggesting that the antigens were apparently localized in the centrosphere. Centrospheres prepared from isolated spindles by salt extraction strongly reacted with the antibodies. One or two bright dots, which may represent centrioles, were visible in the isolated centrosphere. At the end of mitosis, the antigens again appeared in the newly formed daughter nuclei. Centriole-containing cytasters and centriole-free monasters were parthenogenetically induced in unfertilized eggs (Kuriyama and Borisy, (1983) J. Cell Sci. 61: 175-189). The antibodies stained centers of both the asters whether they contained centrioles or not, indicating that the antibodies recognizes the components of the pericentriolar material.

The predicted amino acid sequence of a centrosphere protein in dividing sea urchin eggs is similar to elongation factor (EF-1 alpha)

Monoclonal antibody (SU5), prepared from isolated mitotic spindles of sea urchin eggs, stained centrospheres preferentially and recognized a 50K (K = 10(3) Mr) polypeptide on immunoblots. Three positive clones were isolated by screening a lambda gt11 cDNA expression library prepared from sea urchin egg mRNA with SU5. One clone containing a 1.8-kb (1 kb = 10(3) base-pairs) insert was selected for further characterization. The beta-galactosidase fusion protein encoded by the cDNA clone had an apparent relative molecular mass of 150K, indicating that the inserted cDNA produced an estimated 34K of polypeptide. A single 2.2-kb RNA transcript was detected in sea urchin embryos using the cDNA clone as a probe. The cDNA fragment was sequenced and the nucleotide sequence was used to predict the amino acid sequence of the open reading frames in the clone. The putative gene product shows striking similarity to the peptide chain elongation factor (EF-1 alpha) from yeast, fungus, shrimp, insect, mouse and human.

Different cytoskeletal organization in two maturation stages of Discoglossus pictus (Anura) oocytes: thickness and stability of actin microfilaments and tropomyosin immunolocalization

In Discoglossus pictus oocytes, the germinative area (GA) contains long and irregular microvilli where actin microfilaments are located. In the egg, the funnel-shaped dimple that originates by invagination of the GA is present. In the dimple both microvilli and microfilament bundles have a very orderly appearance. This report extends previous observations (Campanella and Gabbiani, Gamete Res 3:99-114, 1980) and shows that GA microfilaments are thinner (36 A average) than dimple microfilaments (60 A average), as measured in ultrathin section. Moreover, the interfilament distance is smaller in GA bundles than in the dimple bundles. To get an insight into actin organization in oocytes and eggs, we used an actin-depolymerizing factor (ADF) in which cryostat sections were incubated prior to immunofluorescent staining with antiactin antibodies. The microfilaments of the GA microvilli and partially of the oocyte cortex are resistant to ADF when compared to those in the dimple and the rest of the egg cortex. We also investigated immunocytochemically the presence of tropomyosin and found that this protein is localized in the dimple and in the cortex of oocytes and eggs but is absent in the GA.

Parthenogenesis in Xenopus eggs requires centrosomal integrity

Xenopus eggs are laid arrested at second metaphase of meiosis lacking a functional centrosome. Upon fertilization, the sperm provides the active centrosome that is required for cleavage to occur. The injection of purified centrosomes mimics fertilization and leads to tadpole formation (parthenogenesis). In this work we show that the parthenogenetic activity of centrosomes is inactivated by urea concentrations higher than 2 M. The loss of activity is correlated with a progressive destruction of the centriolar cylinder and extraction of proteins. This shows that centrosomes are relatively sensitive to urea since complete protein unfolding and solubilization of proteins normally occurs at urea concentrations as high as 8-10 M. When present, the parthenogenetic activity is always associated with a pelletable fraction showing that it cannot be solubilized by urea. The parthenogenetic activity is progressively inactivated by salt concentrations higher than 2 M (NaCl or KCl). However, only a few proteins are extracted by these treatments and the centrosome ultrastructure is not affected. This shows that both parthenogenetic activity and centrosomal structure are resistant to relatively high ionic strength. Indeed, most protein structures held by electrostatic forces are dissociated by 2 M salt. The loss of parthenogenetic activity produced at higher salt concentrations, while the structure of the centrosome is unaffected, is an apparent paradox. We interpret this result as meaning that the native state of centrosomes is held together by forces that favor functional denaturation by high ionic strength. The respective effects of urea and salts on centrosomal structure and activity suggest that the centrosome is mainly held together by hydrogen and hydrophobic bonds. The in vitro microtubule nucleating activity of centrosomes can be inactivated at salt or urea concentrations that do not affect the parthenogenetic activity. Since egg cleavage requires the formation of microtubule asters, we conclude that the extracted or denatured microtubule nucleating activity of centrosomes can be complemented by components present in the egg cytoplasm. Both parthenogenetic and microtubule nucleating activities are abolished by protease treatments but resist nuclease action. Since we find no RNA in centrosomes treated by RNase, they probably do not contain a protected RNA. Taken together, these results are consistent with the idea that the whole or part of the centrosome structure acts as a seed to start the centrosome duplication cycle in Xenopus eggs.

Further fractionation of the glycoprotein families of porcine zona pellucida by anion-exchange HPLC and some characterization of the separated fractions

The glycoproteins of porcine zonae pellucidae have been fractionated into three families (PZP1-3) by gel filtration HPLC [Nakano et al. (1987) Biochem. Int. 14, 417-423]. However, they still comprise heterogeneous molecular species differing in electric charge. We found that sulfate, but not phosphate, is contained in PZP1-3 by a simple and rapid method for microanalysis of the anionic groups. These families were efficiently separated into many fractions by anion-exchange HPLC. When elution was performed by stepwise increase in NaCl concentration in 8 M urea/20 mM Tris-HCl, pH 8.0, a single distinctive peak emerged for each step. The analyses of amino acids, monosaccharides, and anions of the eight separated fractions of the major family, PZP3, showed that larger amounts of sulfated lactosamine linked to the constituent proteins are present in the fractions that are eluted later: the chain length and/or the chain number of these polylactosamines and the sulfate content increased with stepwise increase in NaCl concentration. Composition analyses also revealed that twice as much N-glycolylneuraminic acid is present as N-acetylneuraminic acid in all fractions. The contents of these sialic acids in the fractions slightly increased in the order of elution. These results together with those of the analyses of endo-beta-galactosidase digests showed that the charge heterogeneity of the porcine zona proteins is due mainly to differences in the amount of sulfated lactosamine, which is predominantly distributed in the non-reducing regions of the sugar chains.

An inhibitor of T lymphocyte blastogenesis derived from the unfertilized ova of Shad (Alosa sapidissima)

Unfertilized ova from Shad, a North Atlantic herring, contains a cytostatic inhibitor of T lymphocyte blastogenesis. The inhibitor has an estimated molecular weight of 10,000-30,000 Da, is heat stable, non dialyzable, and resistant to protease digestion and periodate oxidation. Although the inhibitor functions at an early metabolic event in T lymphocyte mitogenesis, it does not appear to interfere with thymidine transport, antagonize lectin binding to lymphocyte surface receptors, or interfere with the function of an essential serum component in the cell culture media.

A species-specific sperm-activating peptide from the egg jelly of the sea urchin Diadema setosum

1. A species-specific sperm-activating peptide was isolated from the egg jelly of the sea urchin Diadema setosum and the amino acid sequence was determined as follows: (formula; see text). 2. The peptide caused significant increases of respiration rates and cyclic nucleotide concentrations in D. setosum spermatozoa as low as 10(-9) M. 3. The addition of the peptide to D. setosum spermatozoa resulted in the appearance of a newly stained protein (mol. wt 128,000) on sodium dodecyl sulfate-polyacrylamide gels.

Identification of outer oocyst wall proteins of three Cryptosporidium (Apicomplexa: Cryptosporidiidae) species by 125I surface labeling

Autoradiography of oocyst wall surface proteins of three Cryptosporidium spp. revealed common bands at 285 to 290, 145 to 148, 120, 57, and 32 kilodaltons (kDa). Cryptosporidium baileyi and C. muris share proteins at 180, 100, 80 to 81, 29, and 18 to 19 kDa; C. baileyi and C. parvum share one protein at 46 to 47 kDa; and C. muris and C. parvum share a protein at 67 to 69 kDa. Additional protein bands, each unique to one species, were also observed.

Sea urchin egg mitochondrial DNA contains a short displacement loop (D-loop) in the replication origin region

Based on solution hybridization using single-stranded probes, native mitochondrial DNA extracted from sea urchin eggs contains a displacement-loop (D-loop) of approximately 70-80 nt. This maps to the single extended unassigned sequence of the genome, between the genes for tRNA(thr) and tRNA(pro), which also appears to contain the origin of first-strand replication. The D-loop commences at or close to a site of supercoil-dependent S1 nuclease hypersensitivity, adjacent to a run of 20 consecutive C residues, terminates near to the boundary of tRNA(thr), and appears to be composed at least partly of RNA, based on the sensitivity of the assays to RNase H. These experiments imply that the mechanisms of replication initiation in sea urchin and vertebrate mtDNAs are very similar, and suggest that the developmental restriction on mtDNA synthesis in eggs and embryos is maintained at the level of D-loop extension.

Isolation and structures of glycoprotein-derived free sialooligosaccharides from the unfertilized eggs of Tribolodon hakonensis, a dace. Intracellular accumulation of a novel class of biantennary disialooligosaccharides

Novel acidic oligosaccharides were isolated in abnormally large amounts (about 200 ng/egg) from the unfertilized eggs of Tribolodon hakonensis (a dace, "ugui" in Japanese). The free oligosaccharides were found to consist of a mixture of disialylated species most of which end with beta-mannosyl N-acetylglucosamine structure at their reducing termini, i.e. greater than Man beta 1-4GlcNAc. A minute portion of the sialooligosaccharides was found to have the reducing terminal structure, di-N-acetylchitobiose, i.e. greater than Man beta 1-4GlcNAc beta 1-4GlcNAc. From the structural analysis of these free sialooligosaccharides, the following structures are proposed: (sequence; see text) Occurrence of such a symmetrically or dissymmetrically branched form of the biantennary nonreducing periphery as revealed here is novel. Although it is unknown why and how such high amounts of free oligosaccharides are accumulated in unfertilized eggs, these were presumably protein-linked components and must be released at certain stages of oogenesis.

Cold shock induces actin reorganization and polyspermy in sea urchin eggs

The effect of low temperature on the cortical actin system and polyspermy in sea urchin eggs was studied. Eggs cold-shocked at 3 degrees C for 1 hour formed a cortical system of polymerized actin and were polyspermic when fertilized. These effects were completely reversible following a 7-20 minute recovery period at room temperature. The present data raises the possibility that actin, or components of the egg cytoskeleton, regulate sperm entry in sea urchin eggs.

Quantitative X-ray microanalysis of calcium in sea urchin eggs after quick-freezing and freeze-substitution. Validity of the method

Freeze-substitution was used to study the distribution of calcium in sea urchin eggs, and the validity of the technique was assessed. We followed the fate of both total and exchangeable calcium of sea urchin eggs in two species (Paracentrotus lividus and Arbacia lixula) after the various treatments needed for freeze-substitution and embedding. We compared the calcium content either by X-ray microanalysis of Epon-embedded sections of freeze-substituted eggs (6.2 +/- 0.71 mmoles/kg of Epon-embedded tissue) or by flame spectrometry analysis of living eggs (32.3 +/- 1.30 nmoles/mg protein). After standardization of units, both values lead to similar total calcium content. We also measured the movements of 45Ca from prelabelled eggs. Exchangeable 45Ca as well as total calcium appeared unaffected by the preparative treatment for X-ray microanalysis. In conclusion, our preparative technique for X-ray microanalysis can be considered appropriate for our material and allows us to undertake a subcellular quantification of calcium in various organelles.

Structural studies of fertilization-associated carbohydrate-rich glycoproteins (hyosophorin) isolated from the fertilized and unfertilized eggs of flounder, Paralichthys olivaceus. Presence of a novel penta-antennary N-linked glycan chain in the tandem repeating glycopeptide unit of hyosophorin

New glycoproteins of 100-120 kDa were isolated from the unfertilized eggs of flounder, Paralichthys olivaceus. Compositionally indistinguishable glycopeptides of 6 kDa were also purified from the activated or fertilized eggs. These high and low molecular mass glycoproteins are characterized by high (about 85%) carbohydrate content. Although some heterogeneities exist in the amino acid sequences, the 6-kDa glycopeptides (decapeptides with single large N-linked glycan chains), isolated from the fertilized eggs are the repeating units of the high molecular mass glycoproteins. As judged from several distinctive features the 100-120-kDa glycoproteins are apparently major components of cortical alveoli of flounder eggs and are regarded as members of glycoproteins we have defined under the name of "hyosophorin" (Kitajima, K., Inoue, S., and Inoue, Y. (1989) Dev. Biol. 132, 544-553). Composition analysis, Smith degradation, hydrazinolysis-nitrous acid deamination, permethylation analysis, and 400-MHz 1H NMR spectroscopy provided evidence for the structure of a novel penta-antennary glycan chain attached to the repeating unit (decapeptide) of the protein core. The structure thus determined is: (Formula: see text). The presence of a unique class of carbohydrate-rich glycoproteins (H-hyosophorin) in the unfertilized eggs, their conversion to the repeating unit (L-hyosophorin) at fertilization, and the finding of a free glycan chain that was formed by scission between the GlcNAc and Asn residues of L-hyosophorin, in the fertilized eggs including embryos of 4-11-h postinsemination, support the view that these molecules may be important in fertilization and subsequent development.

Fractionation of cytostatic factors from cytosols of amphibian eggs

The cytoplasm or cytosols of unfertilized amphibian eggs contain cytostatic factor (CSF) which arrests cleavage at metaphase after injection into a zygote. After addition of Ca2+ to cytosols, the initial CSF (CSF-1) is inactivated, yet CSF develops again during storage at 2 degrees C (CSF-2). We have separated the two CSFs by ultracentrifugation and ammonium sulfate fractionation using Rana pipiens egg cytosols. CSF-1 was sedimented by ultracentrifugation. After Ca2+ addition, the lighter fractions could develop CSF-2, which was also sedimented by centrifugation. The specific activity of CSF-1 was increased in 20-30% AmS fractions, but was not enhanced further by NaF and/or ATP. CSF-2 could develop only in AmS fractions of fresh cytosols above 50% saturation which were devoid of CSF-1 and was reprecipitated from these fractions with AmS at 20-40% saturation with a 30 X increase in specific activity. CSF-2 development did not require ATP, but its rate increased with increasing temperature and was maximum around pH 5.5. These results show that CSF-1 and CSF-2 are separate entities and that CSF-2 is assembled from inactive precursors into an active, larger molecule.

Purification and characterization of a cortical secretory vesicle membrane fraction

A membrane fraction has been prepared by sucrose density gradient fractionation of purified cortical secretory vesicles from the eggs of the sea urchin Strongylocentrotus purpuratus. The purified cortical vesicle membrane fraction has a phospholipid to protein ratio of 1.76 and exhibits a morphology typical of biological membranes as seen by electron microscopy. The protein composition of the purified membranes was analyzed by SDS-polyacrylamide gel electrophoresis and shown to be distinct from that of eggs, cell surface complex, cortical vesicles, fertilization product, and yolk platelets. Alkaline extraction (pH 11.0) of peripheral membrane proteins increased the phospholipid to protein ratio to 2.55 and removed several polypeptides. Immunoblot analysis of the isolated cortical vesicle membrane fraction revealed low levels of contamination with two major cortical vesicle content proteins. Fractions enriched in egg plasma membranes and yolk platelet membranes also have been isolated and compared with the cortical vesicle membranes by SDS-polyacrylamide gel electrophoresis. The protein compositions of the three membrane fractions were found to contain very little overlap, indicating that the cortical vesicle membrane preparation is relatively free of contamination from these likely noncortical vesicle sources of membrane. Both the plasma membrane and cortical vesicle membrane samples were found by immunoblotting to contain actin.

A novel plaque assay system for paramyxoviruses

A combination of 5% allantoic fluid and 200 micrograms/ml DEAE-dextran with 30 mM MgCl2 used as a supplement to normal overlay medium was found to give large, clear plaques on monolayers of secondary chick embryo fibroblasts infected with avirulent strains of Newcastle disease virus which did not produce plaques without these additions. This modified overlay also allowed plaque assay of Sendai virus strain Z, and avoided any requirement for special cell lines or the use of serum-free medium.

The effect of chronic lead intoxication in mature chickens

In a study of chronic lead intoxication in mature chickens, blood lead levels were significantly lower in hens than in roosters receiving the same oral dose of lead. It was then shown that eggshells from lead-treated hens contained 6-12 times the lead concentration of eggshells from control hens. Similarly, the lead content of egg yolks from treated hens was significantly higher than yolks from controls. Lead-treated hens laid significantly more eggs during the period of observation of nearly 3 years because of the increased frequency of laying cycles, which was almost three times that of control hens. A further observation was histologic damage to the mature testes of the rooster.

Amounts and modulation of actin mRNAs in mouse oocytes and embryos

In order to measure the content of beta- and gamma-actin mRNA in mouse oocytes and ovulated eggs, Northern and slot blots were hybridized to complementary RNA probes transcribed from mouse isotype-specific cDNA sequences. The blots included samples of isotype-specific sense strand RNA standards prepared from the same cDNA sequences. Total actin mRNA content was estimated to be 40 fg per preovulatory full-grown oocyte or egg, consisting of one-third beta-actin mRNA and two-thirds gamma-actin mRNA. Ninety per cent of the actin mRNA is on polysomes in full-grown oocytes. The per cent of actin mRNA in polysomal mRNA is similar to the per cent of actin in newly synthesized proteins. Measurements on other developmental stages showed that, in mid-growth-phase oocytes, each actin mRNA reaches a level twofold higher than in full-grown oocytes. Thereafter, all modulations of the two isotypic mRNAs occur in parallel; that is, they are maintained at constant levels during the late growth phase (oocytes from females 8–14 days old); gradually degraded in oocytes that have completed their rapid growth phase (oocytes from females 15–18 days old), in maturing oocytes, and in 1- and 2-cell embryos; and deadenylated after about 7 h of progression into meiotic maturation.

Analysis of supra-nucleosome particles from unfertilized eggs of sea urchins

Two discrete supranucleosomal particles that differ in their electrophoretic migration on 1% agarose gels were isolated from unfertilized sea urchin eggs. Both particles contain the same complement of cleavage stage (CS) chromosomal proteins, which is identical to the complete set of basic proteins isolated directly from chromatin by extraction with 0.25 N HCl. DNA fragments between 210 and 1500 bp were found in both particles, and the basic unit of DNA repeat length determined by micrococcal nuclease digestion was 126 +/- 3 bp. The isolated nucleoparticles are electrophoretically stable over a wide range of DNA sizes (126-1500 bp) indicating that their structure is maintained by internal interactions among the CS chromosomal proteins, previously designated CS A through CS G. Based on these results we conclude that the CS chromosomal proteins are functionally equivalent to classical histones in their ability to direct higher ordered structures of chromatin.

Genes for extracellular-matrix-degrading metalloproteinases and their inhibitor, TIMP, are expressed during early mammalian development

Extracellular matrix (ECM) remodeling accompanies cell migration, cell-cell interactions, embryo expansion, uterine implantation, and tissue invasion during mammalian embryogenesis. We have found that mouse embryos secrete functional ECM-degrading metalloproteinases, including collagenase and stromelysin, that are inhibitable by the tissue inhibitor of metalloproteinases (TIMP) and that are regulated during peri-implantation development and endoderm differentiation. mRNA transcripts for collagenase, stromelysin, and TIMP were detected as maternal transcripts in the unfertilized egg, were present at the zygote and cleavage stages, and increased at the blastocyst stage and with endoderm differentiation. These data suggest that metalloproteinases function in cell-ECM interactions during growth, development, and implantation of mammalian embryos.

Quantitation and subcellular localization of proliferating cell nuclear antigen (PCNA/cyclin) in oocytes and eggs of Xenopus laevis

Proliferating cell nuclear antigen (PCNA/cyclin) is a 36-kDa polypeptide present in the nuclei of mitotically active cells. It is known to be involved in DNA replication through an association with DNA polymerase delta. We examined the total content as well as the subcellular distribution of PCNA in the oocyte and the egg of Xenopus laevis by employing immunocytological staining and immunoblot analysis. While oocytes are not capable of replicating chromosomes, PCNA is abundant in the nucleus (about 65 ng per nucleus). The oocyte cytoplasm, on the other hand, does not contain a significant quantity of this protein. The amount of total PCNA does not change appreciably during oocyte maturation and the subsequent stages of egg cleavage. Thus, PCNA belongs to a class of proteins which are stockpiled during oogenesis in order to be utilized later for early embryogenesis.

Bacterial action of fertilization envelope extract from eggs of the fish Cyprinus carpio and Plecoglossus altivelis

The vitelline envelope (VE) and fertilization envelope (FE) in eggs of the fish Cyprinus carpio and Plecoglossus altivelis were purified by homogenization of eggs or embryos in 5 mM Tris-HCl buffer, pH 7.0, containing 2 mM ethylenediamine tetraacetic acid disodium salt (EDTA), except for processing of VEs in Plecoglossus eggs, and by repeated washing wih the same buffer. To extract the outermost layer material, the purified VEs and FEs were processed overnight at 4 degrees C in 5 mM Tris-HCl buffer, pH 7.0, containing 8 mM 2-mercaptoethanol, 2 mM EDTA, 0.3 M alpha-lactose, 0.3 M glucose, and 0.9% NaCl. Since extraction of the outermost layer of the VEs of Cyprinus eggs in this solution was found to be ultrastructurally incomplete, further sonication in the same buffer was necessary. The solution extracted from purified VEs or FEs was dialyzed against 5 mM Tris-HCl buffer, pH 7.0, followed by lyophilization. The extracts from the FEs from both fish species contained two kinds of lectins, one agglutinated human B-type erythrocytes and the other nonspecifically agglutinated fish spermatozoa, and both extracts had a strong bactericidal effect on Vibrio anguillarum that was isolated from diseased cultured fish, but not on Aeromonas hydrophila and Escherichia coli. The extracts of purified VEs from eggs of both fish had no bactericidal effect on the bacteria examined, nor any agglutination effect on human erythrocytes and fish spermatozoa.

Isolation and characterization of a novel type of sialoglycoproteins (hyosophorin) from the eggs of medaka, Oryzias latipes: nonapeptide with a large N-linked glycan chain as a tandem repeat unit

We found a novel type of sialoglycoprotein (SGP) with apparent molecular mass ranging from 15,000 to 100,000 Da in the unfertilized eggs of the medaka fish, Oryzias latipes. From fertilized eggs we isolated the corresponding sialoglycopeptides of apparent molecular weight 7000. The amino acid and carbohydrate compositions of these glycoproteins and glycopeptides are very similar, if not identical, and they contain 90%, by weight, of carbohydrate, the predominant sugars being Gal, GlcNAc, and NeuAc. The chemical and physical data indicate that 15- to 100-kDa SGPs are made up of tandem repeat structures whose repeating unit is 7-kDa sialoglycopeptide, and, upon fertilization, higher molecular weight SGPs undergo proteolytic depolymerization to the least structural unit, 7-kDa sialoglycopeptide. As is the case with polysialoglycoproteins (PSGP) found in salmonid fish eggs, a novel family of sialoglycoproteins has been proven to be a major component of cortical alveoli of medaka eggs, namely, hyosophorin. However, we found that they differ markedly from PSGPs (salmonid fish egg hyosophorins) in terms of the carbohydrate composition. The chemical composition and the results of Smith degradation indicate that SGP contains one large N-linked glycan chain per repeat unit. We have determined the amino acid sequence of 7-kDa sialoglycopeptide: Asp-Ala-Ala-Ser-Asn*-Gln-Thr-Val-Ser, where * indicates the asparagine residue to which a large glycan chain consisting of Fuc2Man3Gal15GlcNac9NeuAc6 is attached. The direct experimental evidence for the presence of a polyprotein structure suggests that the covalent nature of the higher molecular weight SGPs should be expressed as [Asp-Ala-Ala-Ser-Asn*-Gln-Thr-Val-Ser]N, where N = 2 to 14 but for the major fraction N = 12.

A tumor growth inhibitory factor and a tumor growth promoting factor isolated from unfertilized ova of shad (Alosa sapidissima)

In the present study, a cytostatic tumor growth inhibitory peptide and a tumor growth promoting peptide with molecular weights of 20,000-30,000 Da have been identified in the supernatant fraction of unfertilized ova from Shad. The factors can be separated by gel chromatography, thus indicating that the factors are individual molecules. Both of the factors are nondialyzable, heat stable, and resistant to trypsin digestion and periodate oxidation.

Distribution of ion channels in ascidian eggs and zygotes

Ascidian eggs and zygotes were whole-cell voltage-clamped and inward membrane currents, generated by stepping the membrane potential, studied from fertilization up to cytokinesis. Currents, induced by changing the voltage in steps from -80 to -30 mV, or to 0 mV, had maximum amplitudes which ranged from 400 to 1200 pA in the unfertilized egg and 100 to 1300 pA in the zygote. At 5 to 10 min after fertilization it was not possible to generate inward currents owing to the activity of nonspecific fertilization channels. Preceding cytokinesis, we observed a reduction in amplitude of the inward currents. By cutting eggs and zygotes into fragments, we have shown that the ion channels generating these inward currents are symmetrically distributed over the egg plasma membrane, but regionalized in the zygote with a maximum density at the animal pole.

Calmodulin-binding proteins are developmentally regulated in gametes and embryos of fucoid algae

Calcium-binding proteins and calmodulin-binding proteins were identified in gametes and zygotes of the marine brown algae Fucus vesiculosus, Fucus distichus, and Pelvetia fastigiata using gel (SDS-PAGE) overlay techniques. A calcium current appears to be important during cell polarization in fucoid zygotes (K.R. Robinson and L.F. Jaffe, 1975, Science 187, 70-72; K.R. Robinson and R. Cone, 1980, Science 207, 77-78), but there are no biochemical data on calcium-binding proteins in these algae. By using a sensitive 45Ca2+ overlay method designed to detect high-affinity calcium-binding proteins, at least 9-11 polypeptides were detected in extracts of fucoid gametes and zygotes. All samples had calcium-binding proteins with apparent molecular weights of about 17 and 30 kDa. A 17-kDa calcium-binding protein was purified by calcium-dependent hydrophobic chromatography and was identified as calmodulin by immunological and enzyme activator criteria. A 125I-calmodulin overlay assay was used to identify potential targets of calmodulin action. Sperm contained one major calmodulin-binding protein of about 45 kDa. Eggs lacked major calmodulin-binding activity. A 72-kDa calmodulin-binding protein was prominent in zygotes from 1-65 hr postfertilization. Both calmodulin-binding proteins showed calcium-dependent binding activity. Overall, the data suggest that the appearance and distribution of certain calcium-binding and calmodulin-binding proteins are under developmental regulation, and may reflect the different roles of calcium during fertilization and early embryogenesis.

Variability in electrophoretic mobility of Gi-like proteins: effect of SDS

Two forms of Gi-like protein are resolved in both somatic cells and mouse gametes when Sigma SDS (95% grade) is used during polyacrylamide gel electrophoresis, whereas only a single species is resolved when Bio-Rad SDS (electrophoresis grade) is used. These two Gi-like proteins are likely to reflect two distinct species, since (i) the two species resolved in the presence of Sigma SDS migrate with the same electrophoretic mobility upon re-electrophoresis in the presence of Sigma SDS and (ii) exchanging Sigma SDS for Bio-Rad SDS resolves a single species, whereas exchanging Bio-Rad SDS for Sigma SDS resolves two species.

Tropomyosin in the sea urchin egg cortex

Tropomyosin was purified from the Triton-treated cortex fraction of fertilized sea urchin egg. Egg tropomyosin showed characteristics typical of nonmuscle tropomyosins such as low molecular mass, short periodicity of Mg2+-paracrystals, low lysine/arginine ratio, high Mg2+ requirement in binding to F-actin, in addition to the properties of all tropomyosins, namely, stability to high temperature, anomalous migration of SDS/urea gel, dissociation from F-actin under high ionic conditions and very acidic isoelectric point. Co-sedimentation assay of egg tropomyosin with actin in the presence of the previously purified high-molecular-mass actin binding protein (260-kDa protein) showed that these two proteins bind to actin filaments in a non-competitive manner. This suggested that both the proteins play a cooperative role in the formation of actin-filament-based cytoskeletal structure in the cortex.

225-Kilodalton phosphoprotein associated with mitotic centrosomes in sea urchin eggs

Protein phosphorylation during development of sea urchin eggs from fertilization to first cleavage was examined by labeling cells with specific antiphosphoprotein antibodies. Indirect immunofluorescence staining with monoclonal antithiophosphoprotein antibody (Gerhart et al.: Cytobios 43:335-347, 1985) has revealed that nuclei as well as centrosomes, kinetochores, and midbodies were specifically thiophosphorylated in developing eggs incubated with adenosine 5'-O (3-thiotriphosphate) (ATP-gamma-S). The phosphorylation reaction required Mg2+ but was not dependent on cAMP or calmodulin in detergent-extracted models. Centrosomes were purified by fractionation of isolated mitotic spindles with 0.5 M KCl extraction. The thiophosphoproteins were retained in the purified centrosomes and the antibody recognized a major 225-Kd polypeptide on immunoblots. In an independent preparation, a monoclonal antiphosphoprotein antibody (CHO3) was found also to react with mitotic poles and stained a 225-Kd polypeptide, confirming the centrosome specificity of this protein. Immunoelectron microscopy showed that the 225-Kd thiophosphoprotein was found at mitotic poles associated with granules to which mitotic microtubules were directly attached. Unlike centrosomes in permeabilized eggs, those in isolated spindles could not be thiophosphorylated, possibly due to inactivation or loss of either phosphorylation enzymes or cofactors, or both, during isolation. The immunofluorescence labeling of thiophosphate could be inhibited by ATP and AMP.PNP in a concentration-dependent manner. Exogenous ATP could abolish thiophosphate-staining more effectively when added with phosphatase inhibitors, suggesting a dynamic state in which centrosomal proteins are being phosphorylated and dephosphorylated in rapid succession by the action of protein kinase(s) and phosphatase(s).

Use of a bacteriophage-derived endo-N-acetylneuraminidase and an equine antipolysialyl antibody to characterize the polysialyl residues in salmonid fish egg polysialoglycoproteins. Substrate and immunospecificity studies

Polysialoglycoproteins (PSGP), a class of glycoproteins containing oligo(poly)sialylglycan chains, are the major glycoprotein components in cortical alveoli of a number of Salmonidae fish eggs. Lake trout, Salvelinus namaycush, egg PSGP (PSGP(Sn)) differs from rainbow trout, Salmo gairdneri, egg PSGP (PSGP(Sg)) in its sialic acid composition; the former contains both N-acetyl- and N-glycolyl-D-neuraminic acid residues, designated Neu5Ac and Neu5Gc, while the latter contains only Neu5Gc residues. Fragmentation analysis of oligo(poly)sialyl chains in lake trout PSGP(Sn) has established that there are two distinct types of oligo(poly)sialyl structures in this PSGP molecule, namely alpha-2,8-linked oligo/poly(Neu5Ac) and alpha-2,8-linked oligo/poly(Neu5Gc). No hybrid structure having both Neu5Ac and Neu5Gc residues in the fragment oligosialic acids was detected. These two distinct PSGP preparations from eggs of lake trout and rainbow trout have been used to compare their immunoreactivity with anti-polysialyl antibodies (H.46) and sensitivity to a bacteriophage-derived (Escherichia coli K1F) endo-N-acetylneuraminidase (Endo-N). H.46 was found to cross-react only with lake trout PSGP(Sn) in immunodiffusion assays but not with rainbow trout PSGP(Sg), indicating that H.46 is a specific probe for alpha-2,8-linked poly(Neu5Ac) but not for poly(Neu5Gc). In contrast, Endo-N was found to catalyze the hydrolysis of both alpha-2,8-linked poly (Neu5Ac) and poly(Neu5Gc), so that this enzyme can be used as a diagnostic reagent for detecting both types of polysialic acids. H.46 was used in indirect immunofluorescence experiments to localize PSGP(Sn) in cortical alveoli isolated from lake trout eggs.

The amino acid sequence, immunofluorescence and microinjection studies on the 15 kDa calcium-binding protein from sea urchin egg

The 15 kDa protein is the most abundant low molecular weight Ca2+-binding protein, different from calmodulin, in eggs of sea urchin, Hemicentrotus pulcherrimus. The data from the amino acid sequence demonstrated that the 15 kDa protein belonged to the troponin C superfamily. Based on immunofluorescent and immunomicroscopic observations, we showed that the 15 kDa protein localized in the nuclei of fertilized eggs and mitotic apparatus of dividing eggs. Microinjection of the antibody against 15 kDa protein into sea urchin blastomeres resulted in the arresting of cell division. These results suggest that the 15 kDa protein plays an important role in mitosis of sea urchin egg.

The dorsal protein is distributed in a gradient in early Drosophila embryos

dorsal is one of the maternally active dorsal-ventral polarity genes of Drosophila and is closely related to the vertebrate proto-oncogene c-rel. Genetic experiments suggest that dorsal represents one of the last (if not the last) steps in the maternal pathway involved in establishing dorsal-ventral polarity in the early embryo. Even though the dorsal RNA is uniformly distributed in the embryo, we have found that the dorsal protein is specifically localized in peripheral nuclei of syncytial and cellular blastoderm stage embryos, and it is distributed in a ventral-to-dorsal gradient. These findings suggest possible mechanisms for how the dorsal protein may communicate maternal positional information to the zygotic genome.

Modification of porcine zona pellucida with fluorescein isothiocyanate: evidence for the presence of a structural unit consisting of glycoproteins in the mammalian egg coat

Intact porcine ova and mechanically isolated zonae pellucidae from the ova were treated with a limiting amount of FITC in isotonic solutions at different pHs. The modified zona proteins were fractionated into three families (FTC-PZP1-3) by HPLC on a gel filtration column. It was found by this HPLC that the amino groups of PZP3 hardly reacted with FITC, whereas those of PZP1 and 2 fairly reacted, reflecting the organization of these families in the zona structure. The difference in reactivity of the three families with FITC suggested the presence of a structural unit in the zona, thus supporting the filamentous model of Wassarman.

Melibiosylceramide as the sole ceramide dihexoside from the eggs of the sea urchin, Anthocidaris crassispina

Melibiosylceramide (Gal alpha 1-6Glc beta 1-1Cer) was found as the sole ceramide dihexoside from the eggs of the sea urchin, Anthocidaris crassispina. Ceramide monohexoside of the eggs consisted only of glucosylceramide (Glc beta 1-1Cer). These lipids were purified by successive column chromatographies on DEAE-Sephadex A-25, silicic acid and Florisil, and identified by gas-liquid chromatography, negative-ion fast atom bombardment mass spectrometry and proton nuclear magnetic resonance spectroscopy as well as methylation analysis. Long-chain base compositions of both lipids were almost identical and comprised n-C18-phytosphingosine and small amounts of its homologs (C17-C19). Fatty acid compositions were qualitatively very similar, but the glucosylceramide contained more 2-hydroxy fatty acid than the melibiosylceramide. Although the chain length of fatty acids was distributed over a wide range, six major fatty acids, namely 22:1, 23:1, 24:1, 22h:1, 23h:1 and 24h:1, constituted more than 92% of the fatty acid content in these lipids.

Molecular changes in the human zona pellucida associated with fertilization and human sperm-zona interactions

The zona pellucida (ZP) is a specialized extracellular matrix surrounding the mature oocyte. Specific functions ascribed to the ZP include sperm-binding, induction of the acrosome reaction, and involvement in the "slow block" to polyspermy. We have examined the ZP from a variety of human eggs recovered from follicular aspirates. Mechanically isolated ZP were heat-solubilized, iodinated, and characterized by SDS-PAGE. Under nonreducing conditions, the human ZP is characterized by two species of 92-120K (ZP1,2) and 57-73K (ZP3). After reduction, ZP1,2 separates into two components of 97K (ZP1) and 82K (ZP2), with ZP3 at 70K. Under reducing conditions, ZP specifically isolated from fertilized eggs reveals approximately equal proportions of all three iodinated ZP molecules. However, ZP specifically isolated from fertilized eggs reveals a substantial disappearance of ZP1. The ZP from unfertilized eggs does not display this modification of ZP1, even when solubilized zonae are co-incubated with sperm or sperm lysates. We suggest that this molecular change in ZP1 is a direct result of the egg cortical reaction. This demonstrates, for the first time, structural changes in the human ZP directly associated with fertilization. In additional studies, we have demonstrated that capacitated human sperm can be saturated with heat-solubilized ZP, demonstrating the presence of human ZP-binding proteins, and that the binding characteristics of zonae isolated from nonfertilized and fertilized eggs differ. Human sperm proteins having an affinity for solubilized zonae have also been identified at 16K, 18K, 19K, 35K, and 60K.

Protein tyrosine phosphorylation in response to fertilization

The sea urchin egg contains one or more protein tyrosine kinases which are active during the response of the egg to fertilization. In the present study, we have used an antibody specific for phosphotyrosine to determine which egg proteins are phosphorylated on tyrosine in response to fertilization. Analysis of immunoblots prepared from fertilized and unfertilized eggs revealed that fertilization results in a major increase in the phosphotyrosine content of a 350-kDa egg protein. Increased phosphorylation of this protein was detected as early as 1 min after fertilization, at which time it represented the most prominent phosphotyrosine containing protein in the egg. Tyrosine phosphorylation of this protein was transient however, and after 5 min post-insemination, the protein was dephosphorylated or otherwise degraded. Egg membrane proteins of approximately 40, 75, and 145 kDa were also found to act as substrates for protein tyrosine kinases in vitro, but did not exhibit significant changes in phosphotyrosine content during egg activation.

Comparative structures of the apopolysialoglycoproteins from unfertilized and fertilized eggs of salmonid fishes

The complete amino acid sequence of the major polysialoglycoproteins (PSGPs) from two genera of salmonid fish eggs, Salvelinus and Oncorhynchus, has been determined. The occurrence of tandem repeats of a genus-specific dodeca- and tridecapeptide was found for the apoPSGP of Salvelinus leucomaenis pluvius (Slp) and Oncorhynchus masou ishikawai (Omi), respectively, their amino acid sequences being highly homologous with that of rainbow trout [Salmo gairdneri (Sg)] apoPSGP (*denotes the glycosylation site; mean value of N = approximately 25): H-PSGP(Slp): (Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-)N H-PSGP(Omi): (Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Ser-)N H-PSGP(Sg): (Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Gly-)N Within 5-7 min following fertilization H-PSGP is converted to the low-molecular-mass PSGP (L-PSGP) by a specific protease (PSGPase). We have purified L-PSGP from the fertilized eggs of S. leucomaenis pluvius and Oncorhynchus keta (chum salmon) and compared it with rainbow trout egg L-PSGP(Sg) by analysis of their amino acid sequence: L-PSGP(Slp): Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Asp L-PSGP(Ok): Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Ser L-PSGP(Sg): Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Gly The data support the conclusion that H-PSGP is degraded in vivo 5-7 min after fertilization to L-PSGP by proteolytic cleavage at the position two residues C-terminally to the Pro residue, i.e., -Pro-Ser-Xaa-Asp-(Xaa = either Gly, Ser, or Asp) by the action of PSGPase.

Monoclonal antibodies specific for thiophosphorylated proteins recognize Xenopus MPF

Maturation promoting factor, (MPF), is a crucial regulatory component of the eukaryotic cell cycle. Though it is ubiquitous, MPF has been difficult to purify to homogeneity, and little is known about its physical properties or composition. In an attempt to further characterize and purify this protein, we have isolated five monoclonal antibodies that immunoadsorb MPF activity, and inhibit the activity in solution. However, all the antibodies recognize many proteins in partially purified MPF. We have shown that antibody binding is dependent on previous exposure of the preparation to ATP gamma S. This suggests that the antibodies specifically recognize thiophosphoproteins, although not all thiophosphorylated proteins in MPF are immunoprecipitated. Using one antibody, MPF was partially purified by immunoadsorption chromatography. These experiments provide the first evidence that MPF from Xenopus is a phosphoprotein that becomes thiophosphorylated upon addition of ATP gamma S.