Systemic plant signal triggers genome instability

Previously, we have shown that infection of tobacco plants with a viral pathogen triggers local and systemic induction of homologous recombination (HR). Here, we have tested the hypothesis of whether free radicals are potentially involved in the induction of the systemic effect. We report a significant induction of HR in tobacco plants treated with radical-generating agents, UVC or rose Bengal (RB). Importantly, the recombination increase was observed in local (treated) as well as systemic (non-treated) tissue. The systemic increase in recombination implies the existence of a signal that is transmitted to non-treated tissue. Several sets of grafting experiments proved the generation of said signal by both RB and UVC exposure. A statistically significant increase in HR was observed in tissue that received a systemic signal via a grafted leaf. Similar data were obtained from transgenic plants naphthalene degrading salicylate 1-hydroxylase (NahG) unable to accumulate salicylic acid (SA). Interestingly, pre-treatment of plants with the radical-scavenging compound N-acetyl-l-cysteine (NAC) led to a significantly lower recombination increase upon grafting after treatment with UVC and RB. Moreover, leaves taken for grafting from NAC-pre-treated plants exhibited a lower level of oxidized organic compounds. Our data suggest the involvement of free radical production in either generation or maintenance of the recombination signal. We discuss potential mechanisms for generation of the signal and possible adaptive advantages of enhanced genomic flexibility following exposure to DNA-damaging agents.     

Redescription of a rare deep-sea batfish, <Emphasis Type="Italic">Halieutopsis bathyoreos</Emphasis> (Lophiiformes: Ogcocephalidae)

Halieutopsis bathyoreos Bradbury, 1988 (Lophiiformes: Ogcocephalidae), previously described only on the basis of the holotype (62.6mm in standard length) from the central North Pacific, is redescribed on the basis of the holotype and six additional specimens (41.2–68.7mm in standard length) collected from the western South Pacific, off Papua New Guinea, and the western North Pacific, including the Japanese Archipelago. Halieutopsis bathyoreos is distinguished from its congeners by having a shelflike rostrum extending anteriorly well beyond the mouth, a dorsal escal lobe slightly bisected ventrally, an illicial cavity square in outline and completely visible in ventral view, and lacking tubercles on the ventral surface of the disk. The following characters are newly added to the diagnoses of this species: rostrum width 21–29% of head length, tubercles on the dorsal surface of the disk about half the diameter of those on the lateral margin, and 13–15 large lateral-line scales on the tail.     

Triamterene-β-cyclodextrin systems: Preparation,characterization and in vivo evaluation

The purpose of this research was to improve the solubility and therefore dissolution and bioavailability of triamterene, a poorly water soluble diuretic, by complexation with β-cyclodextrin. Triamterene has been reported to show low bioavailability after oral administration, with wide intersubject variation. This study presents the formulation of solid dispersions of triamterene with β-cyclodextrin—by cogrinding, kneading, and coevaporation, using low pH conditions—and their characterizations, evaluation of improvement in dissolution profiles, and in vivo advantage. Phase solubility studies indicated complex with possible stoichiometry of 1∶1 and a stability constant of 167.67M⁻¹. The solid dispersions were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, x-ray diffraction, and differential scanning calorimetry studies. The characterization studies confirmed inclusion of the phenyl ring of triamterene within the nonpolar cavity of β-cyclodextrin in the coevaporate. Remarkable improvement in in vitro drug release profiles in 0.1 N HCl and pH 6.8 phosphate buffer was observed with all dispersions, especially the coevaporate. The coevaporate, when administered orally in rats, also exhibited improved in vivo activity, as measured by net sodium ion excretion, as compared with triamterene powder. Thus, coevaporation of the drug and β-cyclodextrin from acidified alcohol provide the optimum condition for inclusion complexation to give a binary system with remarkable improvement in in vitro drug release profile and in vivo performance.     

Monozygotic twinning in rhesus monkeys by manipulation of in vitro-derived embryos

The nonhuman primate is a relevant model for human disease that can be used for diverse biomedical investigations. The ability to propagate a founder animal by application of assisted reproductive technologies is pressing, but an even greater need in many studies is access to genetically identical animals. In an effort to create genetically identical monkeys, we evaluated two approaches to monozygotic twinning; blastomere separation, and blastocyst bisection. Embryos were produced by intracytoplasmic sperm injection of oocytes recovered following controlled ovarian stimulation. The quality of demiembryos produced in these efforts was evaluated by quantitating the efficiency of creating identical pairs for embryo transfer, by morphological assessment, by the allocation of cells to the inner cell mass (ICM) and trophectoderm (TE) in the blastocyst, and by the outcome of embryo transfer to synchronized host animals. Pairs were produced in high yield (85%-95%) by both twinning methods. Demiembryos resulting from blastomere separations at the 2- or 4-cell stage grew to blastocysts at the control frequency. Demiblastocysts contained, on average, half the number of cells of the intact controls while maintaining the same ICM:TE or ICM:total cell ratio. The equivalency of demiblastocysts within a set was also evaluated by differential cell counting. Embryo transfers of identical sets led to a 33% clinical pregnancy rate, with two twin pregnancies initiated. Neither pregnancy resulted in term birth of monozygotic twins, but our results are sufficiently encouraging to justify a large-scale twinning trial in the rhesus macaque.     

Clustering of glycine and NG,NG-dimethylarginine in nucleolar protein C23

Protein C23 (Mr 110 000, pI = 5.5), a major phosphoprotein in the nucleolus of mammalian cells, has been shown to contain 1.3 mol% of NG,NG-dimethylarginine (DMA) [Lischwe, M.A., Roberts, K.D., Yeoman, L.C., & Busch, H. (1982) J. Biol. Chem. 257, 14600-14602]. A tryptic peptide from protein C23 that contains DMA has been isolated and sequenced. Its sequence is Gly-Glu-Gly-Gly-Phe-Gly-Gly-DMA-Gly-Gly-Gly-DMA-Gly-Gly-Phe-Gly-Gly-DMA- Gly-Gly- Gly-DMA-Gly-Gly-DMA-Gly-Gly-Phe-Gly-Gly-DMA-Gly-DMA-Gly-Gly-Phe-Gly-Gly- DMA-Gly-Gly-Phe-DMA-Gly-Gly-DMA-Gly-Gly-Gly-Gly-Asp-Phe-Lys. This peptide contains 34 glycine, 10 DMA, and 6 phenylalanine residues and has clusters of glycine and NG,NG-dimethylarginine interspersed with phenylalanine residues. A similar domain has been found at the amino terminus of a nucleolar protein of Mr 34,000, pI = 8.5. This sequence array may represent a conserved domain characteristic of a certain class of nuclear proteins. All of the methylated arginine residues in protein C23, the 34-kilodalton protein, and myelin basic protein [Carnegie, P.R. (1971) Biochem. J. 123, 57-67] have at least one adjacent glycine. Access of certain arginine methylases to arginine residues may be sterically possible because of the lack of a side chain on the adjacent glycine residue(s).