A repeating fast radio burst associated with a persistent radio source.

The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium1, which is assumed to dominate the total extragalactic dispersion. Although the host-galaxy contributions to the dispersion measure appear to be small for most FRBs2, in at least one case there is evidence for an extreme magneto-ionic local environment3,4 and a compact persistent radio source5. Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift of 0.241 ± 0.001. The estimated host-galaxy dispersion measure of approximately [Formula: see text] parsecs per cubic centimetre, which is nearly an order of magnitude higher than the average of FRB host galaxies2,6, far exceeds the dispersion-measure contribution of the intergalactic medium. Caution is thus warranted in inferring redshifts for FRBs without accurate host-galaxy identifications.

The host galaxy of a fast radio burst.

In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.

ATPase sites in two-headed fragment of Tetrahymena 22S ciliary dynein.

Three-headed Tetrahymena 22S ciliary dynein was found to consist of three heavy chains (HCs) and decompose into two-headed and single-headed fragments upon chymotrypsin digestion. The three HCs (A alpha, A beta, and A gamma) were immunologically different, and presumed to be located on each of the head regions. The two-headed fragment contained A beta and A gamma HCs, while the A alpha HC originated in the single-headed fragment. Both fragments were associated with ATPase activity (Toyoshima, Y. (1987a) J. Cell Biol. 105, 887-895 and Toyoshima, Y. (1987b) J. Cell Biol. 105, 897-901). Using the two-headed dynein fragment, we attempted to determine the site of ATP hydrolysis in the fragment. After digestion of the fragment with 100 micrograms/ml thermolysin for 45 min, we noted eight thermolysin-digested polypeptides (TH 1, 2, 3, 4, 5 alpha, 5 beta, 6 alpha, and 6 beta). By precisely analyzing the degradation process and the products using peptide mapping, immunoblotting and high pressure liquid chromatography, it appeared that the two-headed fragment is dissociated as two separate fragments, each of which contained A beta or A gamma HC. Thermolysin digests, TH 1, 2, 5 alpha and 6 beta were found to be derived from A beta HC, while TH 3, 4, 5 beta and 6 alpha originated in the A gamma HC. Based on the measurements of ATPase activity of these polypeptides, we concluded that the ATPase site is located in the A beta and A gamma HCs, which may have their origins in each head of the two-headed fragment of Tetrahymena 22S ciliary dynein.

Construction of pRES18 and pRES19, Streptomyces-Escherichia coli shuttle vectors carrying multiple cloning sites.

We developed two Streptomyces-Escherichia coli shuttle vectors. The plasmid pRES102, consisting of the essential region of pRES1 and the thiostrepton resistance gene (tsr) fragment of pIJ702, was combined with the E. coli plasmid vector pUC18 or pUC19. The resulting shuttle vectors, designated pRES18 and pRES19, respectively, have relatively compact size (6.25 kb), low copy number, multiple cloning sites reciprocally arranged in opposite directions, and selection markers for both Streptomyces (tsr) and E. coli (beta-lactamase (bla) and beta-galactosidase (lacZ). These shuttle vectors are capable of carrying DNA fragments as long as 10 kb, of being maintained in S. griseus, S. lavendulae and S. lividans, and are compatible with pIJ702.

Cloning of macromomycin apoprotein gene from Streptomyces macromomyceticus by use of 50-mer deoxynucleotide probes.

A mixed probe consisting of two synthetic deoxynucleotides (52 and 54 mers referred to as 50-mer) with arbitrarily chosen C or G for the third letters was prepared based on the amino acid sequences No. 31-48 and No. 72-90 of macromomycin (MCM) apoprotein and successfully used to clone the MCM apoprotein gene. Digestion with Sph I of total DNA of MCM-producing Streptomyces macromomyceticus M480-M1 yielded a 2.6-kb fragment that hybridized strongly to the probes. The hybridized probe was stable to washing with 3 x SSC at 75 degrees C. Radioactivity derived from the hybridized probe was comparable to that expected theoretically from hybridization between the probe and the true target sequence. The 2.6-kb fragment was cloned into Escherichia coli RR1 with pBR322 and subsequently subcloned into Streptomyces lividans TK21 with pIJ702. Nucleotide sequence analysis of the cloned fragment verified the existence of the sequence corresponding to the amino acid sequence of MCM apoprotein and about 90% homologies with the probes. Thus, the use of relatively long deoxynucleotide probes with arbitrarily chosen C or G for the third letters will be advantageous in cloning Streptomyces protein genes where more than 90% of the third letters have been known to be C or G. In addition, theoretical diagnosis of hybridization should be a great help to distinguish true positives from false ones.

The increasing cesarean rate globally and what we can do about it.

Cesarean sections sometimes save the lives of mothers and babies; however, they are excessively used compared to medical necessity, which is influenced by various factors that are explored in this article. Since, in most cases the risks of cesarean sections are greater than the benefits, particularly in cesareans that are not medically indicated, it is astonishing that cesarean surgery is the most common surgical procedure, taking away resources from medically necessary care. While economic incentive is counted among the reasons for the increasing cesarean trend, the situation is not so simple since many factors interact to cause the trend. Since reversal of the vaginal birth after cesarean (VBAC) trend downward is correlated with revised policy statements by e.g. American College of Obstetricians and Gynecologists (ACOG), which have since been partially moderated, it became much more difficult for medical institutions to provide VBACs due to concerns about liability. Although whether to give birth by cesarean delivery is a matter for informed consent, yet childbearing women are influenced significantly by their health service providers' opinions. Even though the World Health Organization (WHO) recommends the most peripheral level of maternity care for normal pregnancy and childbirth that is safe using midwives, yet the percentage of midwife deliveries is low. Among other things, it has been suggested that more childbirth by midwife delivery and in out-of-hospital settings can reduce medically unnecessary cesareans and the undue risks associated with them, and free up medical resources for those in need.

Positive and negative regulation of the transcription of the human protein kinase C beta gene.

To analyze the mechanism of the cell type-specific expression of protein kinase C beta (PKC beta), we isolated the 5'-portion of the human gene for PKC beta and identified multiple positive and negative regulatory sequences that regulate its transcription. S1 nuclease mapping as well as primer extension analysis of the 5'-end of the PKC beta mRNA identified a putative transcriptional initiation site (position +1) 484 base pairs (bp) upstream of the first ATG codon. The 5'-upstream sequence contains a CCAAT sequence at position -110, but no TATA box. The transcriptional activities of various 5'-deletion mutants of the PKC beta gene upstream region, fused to the chloramphenicol acetyltransferase structural gene, were examined in terms of chloramphenicol acetyltransferase expression after transfection into three kinds of rodent cell lines: P19 and GH4C1, which are positive for the expression of PKC beta mRNA; and 3Y1, which is negative. Mutants containing a 5'-flanking sequence longer than 1.9 kilobases (kb) showed chloramphenicol acetyltransferase activities of the same order as the expression of the endogenous gene. This indicates that this region contains sequences regulating the cell-type specificity of PKC beta gene expression and that the specificity is determined at least partially at the level of transcription. The 1.9-kb sequence contains at least three positive elements: P1 (-56 to -234 bp), P2 (-234 to -411 bp), and PN (-1.4 to -1.9 kb). PN is active only in P19 cells, P1 in GH4C1 and P19 cells, and P2 in all three cell lines. In addition to these positive elements, there are negative elements: N1 (-411 to -674 bp), which is active in all three cell lines; and PN, which is active only in GH4C1 cells. These results suggest the presence of multiple trans-acting factors that act on these positive and negative cis-acting elements and regulate the cell type-specific expression of the PKC beta gene.

Activation of R-Ras by Ras-guanine nucleotide-releasing factor.

Ras-GRF/CDC25(Mm), mSos, and C3G have been identified as guanine nucleotide-releasing factors for Ras family proteins. We investigated in this study the guanine nucleotide-releasing activities of Ras-GRF, mSos, and C3G toward R-Ras, which shows high sequence similarity to Ras. Ras-GRF markedly stimulated the dissociation of GDP from R-Ras, and C3G also promoted the release of R-Ras-bound GDP. Under the same conditions, mSos little affected the reaction. When Ras-GRF and R-Ras were coexpressed in COS7 cells, the remarkable accumulation of the active GTP-bound form of R-Ras was observed. C3G also increased active R-Ras in COS7 cells, while mSos did not give any effect. These results indicated that Ras-GRF and C3G could activate R-Ras. Furthermore, the activation of R-Ras by Ras-GRF was enhanced when cells were treated with ionomycin, which is known to increase the intracellular calcium concentration. The examination of tissue distribution of R-Ras, Ras-GRF, and mSos by the reverse transcription-polymerase chain reaction revealed that Ras-GRF was expressed only in brain and testis, whereas R-Ras, C3G, and mSos were expressed rather ubiquitously. These findings raise the possibility that R-Ras is activated by Ras-GRF in brain and testis, and by C3G in other tissues, respectively.

New mu-opioid receptor agonists with piperazine moiety.

New mu-opioid receptor (MOR) agonists containing piperazine and homopiperazine moieties in the structures were synthesized and their affinities to and agonist potencies on MOR were evaluated. Among the synthesized compounds, 4-[4-(2-methoxyphenyl)piperazin-1-yl]-N,N-dimethyl-2,2-diphenylbutanamide (20 Aa) showed the highest affinity to the human MOR expressed in Chinese hamster ovary (CHO)-K1 cells, and the highest agonist potency on the MOR in isolated guinea-pig ileum preparation.

A new old yellow enzyme of Saccharomyces cerevisiae.

In 1993, the first gene of Old Yellow Enzyme (OYE) of Saccharomyces cerevisiae was cloned (Stott, K., Saito, K., Thiele, D. J., and Massey, V. (1993) J. Biol. Chem. 268, 6097-6106) and named OYE2 to distinguish it from the first OYE gene cloned from Saccharomyces carlsbergenesis (Saito, K., Thiele, D. J., Davio, M., Lockridge, O., and Massey, V. (1991) J. Biol. Chem. 266, 20720-20724). The analysis of an OYE2 deletion mutant suggested that S. cerevisiae had at least two OYE genes. In the present study, we cloned a new OYE species named OYE3 and analyzed the OYE3 protein expressed in Escherichia coli. OYE3 consists of 400 amino acid residues and its molecular mass calculated by electrospray mass spectrometry is 44,788 daltons, in good agreement with the value of 44,920 daltons predicted from the amino acid sequence derived from the DNA sequence. In the downstream region of the OYE3 gene, the cytochrome oxidase (COX10) gene exists with a 426-base pair intermediate sequence. Some of the physicochemical and kinetic properties of OYE2 and OYE3 have been determined. Although the two enzymes are clearly closely related, they show differences in ligand binding properties and in their catalytic activities with oxygen and cyclohexen-2-one as acceptors.

Syntheses and antifungal activity of dl-griseofulvin and its congeners. II.

Griseofulvin derivatives, dl-6'-demethyl-6'-ethylgriseofulvin (dl-5) and dl-6'demethyl-6'phenylgriseofulvin (dl-6) were prepared by application of a synthetic method developed by us. Antifungal activity of these derivatives decreased in the order of dl-griseofulvin (dl-1) >> dl-6(inactive). The reaction of these derivatives with ethanethiol gave two types of compounds, 2'-(ethylthio)griseofulvin (15) and 4'-(ethylthio)isogriseofulvin (16). The relationship between the ratios of isolated yield of 15 and 16 and antifungal the activity of griseofulvin derivatives is discussed.

PKCtheta II, a new isoform of protein kinase C specifically expressed in the seminiferous tubules of mouse testis.

Protein kinase C (PKC) theta, a Ca(2+)-independent isoform of PKC, has been known to be expressed in skeletal muscle and T cells. In the present study, we isolated and characterized a smaller transcript expressed in the mouse testis, the cDNA of which is referred hereafter as PKCthetaII and the original PKCtheta as PKCthetaI. The cDNA clone of PKCthetaII has 2184 base pairs and 464 amino acids in the possible open reading frame, consisting of the 5' unique sequence of 20 amino acids and the PKCthetaI sequence of 444 amino acids. Genomic DNA analysis revealed that transcription of PKCthetaII is initiated from the PKCthetaII-specific exon, which is located between exons 7 and 8 of the PKCtheta gene, indicating that alternative splicing is the mechanism by which PKCthetaII is generated. PKCthetaII is expressed exclusively in the testis in an age-dependent manner with sexual maturation. In situ hybridization and reverse transcription-polymerase chain reaction of microdissected tissues clearly demonstrated that PKCthetaII is expressed in the seminiferous tubules of the mouse testis. Consistent with its molecular structure lacking the C1 regulatory domain, PKCthetaII is constitutively active as determined by an in vitro kinase assay, being independent of PKC activators, e.g. phosphatidylserine and phorbol ester. PKCthetaII may play a crucial role in spermatogenesis or some related function of the testis.