Maternal screening and postpartum vaccination for measles infection in Japan: a cohort study.

We investigated the prevalence of measles-sensitive pregnant women and the clinical usefulness of measles vaccination in postpartum women. Measles antibody levels were measured in 751 pregnant women. Forty-four women were vaccinated postpartum, and screened for antibody levels and adverse effects 1 month after vaccination. The prevalence of measles-sensitive pregnant women was 10-20%, with the highest prevalence in those under 24 years of age. Almost all (97.7%) vaccinated women acquired immunity, and did not show any adverse effects. Serum measles antibody levels should be determined in all pregnant women as a screening tool,and sensitive women should be vaccinated immediately after delivery.

Biologically active BMP-2 in early Xenopus laevis embryos.

In this study, we attempted to purify the dimeric BMP-2 from extracts of Xenopus embryos in order to show the presence of BMP-2 activity in the embryos. Immunoreactive BMP-2 protein was found to be a homodimer of an 18 kDa BMP-2 polypeptide linked through disulfide bridge(s). Biological activities of the partially purified dimeric BMP-2 were examined in vitro. The Xenopus BMP-2 induced alkaline phosphatase in a dose-dependent manner in cultured osteoblastic cells, MC3T3-E1. The inducing activity was synergistically enhanced by the presence of retinoic acid. The results showed that the dimeric form of Xenopus BMP-2 has an indistinguishable biological activity from that of mammalian BMP-2.

Biochemical properties of amphibian bone morphogenetic protein-4 expressed in CHO cells.

The biochemical properties of recombinant amphibian bone morphogenetic protein-4 (BMP-4), the cDNA of which has been cloned recently by screening of a Xenopus cDNA library, was characterized. The protein was expressed by the transfection of Chinese hamster ovary (CHO) cells with the cDNA cloned into expression vectors bearing a cytomegalovirus promoter or a simian virus 40 promoter. Northern-blot analysis showed that the latter vector was more efficient for Xenopus BMP-4 expression. Specific antiserum against Xenopus BMP-4 peptide demonstrated that the protein is synthesized as a large precursor, processed to the mature form and then secreted from the cells as a homodimer. Analysis of the biological activity in the conditioned medium revealed that Xenopus BMP-4 has a potent alkaline phosphatase-inducing activity on mouse osteoblastic cells.

Presence of high molecular weight forms of BMP-2 in early Xenopus embryos.

Using polyclonal antibodies which recognize 18 kDa BMP-2, we have previously demonstrated that the major BMP-2 protein in Xenopus embryo extracts is monomeric and not dimerized whereas, the mammalian counterpart derived from bone extract was purified as a dimeric protein. In this study, the same antibodies (Ab383) were used to detect high molecular weight forms of Xenopus BMP-2. Partial purification of the immunoreactive 18 kDa BMP-2 from Xenopus embryo extract by gel filtration, heparin-Sepharose affinity chromatography and preparative SDS-PAGE resulted in co-purification and identification of higher molecular forms of BMP-2 of 110 kDa and 36 kDa. Diagonal SDS-PAGE analysis suggested that they are homodimer and multimer of the 18 kDa species, respectively, linked through disulfide bridge(s).

Genes for bone morphogenetic proteins are differentially transcribed in early amphibian embryos.

We have previously demonstrated that activin, a member of the TGF-beta family, has a potent mesoderm-inducing activity in Xenopus embryos. In the course of screening for activin-related genes from Xenopus, we have cloned cDNAs for Xenopus homologue of BMP-2, -4 and -7. Northern blot analysis revealed that these BMP genes are maternally encoded and differentially regulated after fertilization. Alkaline phosphatase-inducing assay using the recombinant BMP proteins has shown that at least BMP-2 and -4 have similar activity to mammalian counterparts.

Expression of thymosin beta 4 gene during Xenopus laevis embryogenesis.

In order to investigate the molecular events which take place during gastrulation, extracts from developing Xenopus embryos were analyzed for temporal peptide distribution by high performance liquid chromatography. One peptide peak which became increasingly dominant after gastrulation was purified and partially characterized. The amino acid sequence of enzymic digests showed the peptide is extremely similar to mammalian thymosin beta 4. The peptide was capable of binding actin monomers like mammalian counterparts. Cloning of the Xenopus thymosin beta 4 cDNA showed that only three amino acid substitutions occurred between amphibian and bovine. Northern blot analysis revealed the mRNA is maternally present at a low level and the transcript becomes abundant after gastrulation, supporting the distribution of the peptide.

Functional regulation of osteoblastic cells by the interaction of activin-A with follistatin.

A high number of 125I-activin-A binding sites (an apparent Kd of 260 pM and 5,600 sites/cell) were observed on MC3T3-E1 cells, a well characterized osteoblastic cell line. Activin-A has a mitogenic effect on these cells, with the greatest influence being observed on cells in an undifferentiated state, as well as a suppressive effect on the alkaline phosphatase activity. Northern and ligand blotting analyses revealed that these osteoblastic cells produce follistatin, which was down-regulated by retinoic acid treatment. Because follistatin is an activin-A-binding protein, we suggest that activin-A modulates the function of osteoblastic cells by being regulated by follistatin during differentiation.

Identification of bone morphogenetic protein-2 in early Xenopus laevis embryos.

Polyclonal antibodies capable of reacting with amphibian bone morphogenetic protein (BMP-2 and -4) were raised in rabbits by immunization with a synthetic 21 amino acid peptide which corresponds to a sequence residing in the mature protein of Xenopus BMP-2 (xBMP-2). The antibodies recognized an embryonic BMP as well as mammalian and bacteria expressed recombinant xBMPs. The antibodies detected, under reducing conditions, a 30 kDa protein in the extract of oocytes and embryos during early development. Interestingly, acidification of the extract from each developmental stage yielded a protein band of smaller molecular weight of 18 kDa, which is similar in size to reduced form of mature BMPs purified from mammalian species. Two-dimensional electrophoresis employed to examine the molecular weight of unreduced forms using the antibody, revealed that both molecular forms are monomeric in the embryos. The result suggests that at least BMP-2 mRNA previously detected in early embryos, is translated into peptide but the dimerization may be incomplete or strictly limited in these embryos.

Isolation and characterization of recombinant human prorenin in Chinese hamster ovary cells.

Recombinant human prorenin (rh-prorenin) was purified from supernatants of Chinese hamster ovary (CHO) cell line transfected with the cDNA for rh-prorenin by employing a simple two-step procedure which consisted of ammonium sulfate precipitation and immunoaffinity chromatography using a monoclonal antibody specific for the profragment of human prorenin. About 100-fold purification with 35% recovery was achieved after the two steps. Purified rh-prorenin migrated as a single protein band with apparent molecular weights of 46,000-47,000 and about 50,000 on SDS-PAGE and gel filtration (HPLC), respectively, although it consisted of multiple components (pI values, 5.6-6.4) that could be resolved by isoelectric focusing (IEF). The treatment of rh-prorenin with endo-beta-N-acetylglucosaminidase converted the rather broad protein band to a sharp band on SDS-PAGE and reduced the number of multiple pI peaks on IEF. Amino-terminal sequence analysis of both the purified rh-prorenin and rh-renin revealed Leu-Pro-Thr-Asp- and Leu-Thr-Leu-Gly-, respectively, which agreed with those predicted from the base sequences of their cDNA. These data suggested that microheterogeneity of rh-prorenin is due to the carbohydrate moiety, but not to the protein moiety. Purified rh-prorenin was almost inactive, but was cleaved at the carboxyl end of a dibasic pair Lys-2-Arg-1 by trypsin and converted to active renin. However, at the early stage during trypsin activation, new intermediate forms between rh-prorenin and rh-renin were formed, suggesting multiple activation steps of rh-prorenin in addition to the one step activation.

Structure and expression of mouse furin, a yeast Kex2-related protease. Lack of processing of coexpressed prorenin in GH4C1 cells.

We have cloned and sequenced a mouse cDNA encoding the 793-residue amino acid sequence of furin, which is a protein homologous to the yeast Kex2 protease. The entire sequence is 94% identical to that of human furin, and it contains the 289-residue sequence of the subtilisin-like catalytic domain. Within this region, 99, 64, and 53% of the amino acids are identical to those of human furin, human PC2 (the other mammalian Kex2-like protein), and yeast Kex2, respectively. It has been proposed that furin is a mammalian prohormone processing enzyme which cleaves precursors at paired basic amino acids, based on the fact that the Kex2 protease is responsible for processing of alpha-mating factor and killer toxin precursors at dibasic sites. However, Northern blot analysis has revealed that a furin mRNA transcript is present in all tested mouse tissues and culture cell lines, including those known not to process prohormones. Moreover, when furin and a prohormone, prorenin, have been coexpressed in mammalian cells by DNA transfection, no processing has been observed. These observations fail to show a role for furin, a Kex2-like mammalian protease, in prohormone processing.