Restriction enzyme cleavage sites surrounding the structural gene for the lipoprotein of the Escherichia coli outer membrane.

The purified messenger ribonucleic acid (mRNA) for the lipoprotein of the Escherichia coli outer membrane was hybridized with fragments obtained by digestion of E. coli chromosomal deoxyribonucleic acid (DNA) with eight different restriction enzymes. For each restriction enzyme digestion, one specific fragment separated by agarose gel electrophoresis was found to hybridize with the lipoprotein mRNA. From the analysis of restriction fragments generated by double digestions with various combinations of restriction enzymes, cleavage sites for the restriction enzymes near the locus of the lipoprotein structural gene (lpp) were mapped. No restriction fragments of DNA from the E. coli lpp-2 mutant hybridized with the lipoprotein mRNA, confirming that the mutant has a deletion mutation in the vicinity of the lpp gene.     

Pesticide exposure: the hormonal function of the female reproductive system disrupted?

Some pesticides may interfere with the female hormonal function, which may lead to negative effects on the reproductive system through disruption of the hormonal balance necessary for proper functioning. Previous studies primarily focused on interference with the estrogen and/or androgen receptor, but the hormonal function may be disrupted in many more ways through pesticide exposure. The aim of this review is to give an overview of the various ways in which pesticides may disrupt the hormonal function of the female reproductive system and in particular the ovarian cycle. Disruption can occur in all stages of hormonal regulation: 1. hormone synthesis; 2. hormone release and storage; 3. hormone transport and clearance; 4. hormone receptor recognition and binding; 5. hormone postreceptor activation; 6. the thyroid function; and 7. the central nervous system. These mechanisms are described for effects of pesticide exposure in vitro and on experimental animals in vivo. For the latter, potential effects of endocrine disrupting pesticides on the female reproductive system, i.e. modulation of hormone concentrations, ovarian cycle irregularities, and impaired fertility, are also reviewed. In epidemiological studies, exposure to pesticides has been associated with menstrual cycle disturbances, reduced fertility, prolonged time-to-pregnancy, spontaneous abortion, stillbirths, and developmental defects, which may or may not be due to disruption of the female hormonal function. Because pesticides comprise a large number of distinct substances with dissimilar structures and diverse toxicity, it is most likely that several of the above-mentioned mechanisms are involved in the pathophysiological pathways explaining the role of pesticide exposure in ovarian cycle disturbances, ultimately leading to fertility problems and other reproductive effects. In future research, information on the ways in which pesticides may disrupt the hormonal function as described in this review, can be used to generate specific hypotheses for studies on the effects of pesticides on the ovarian cycle, both in toxicological and epidemiological settings.     

Avian biodiversity in the coastal wetlands of the Okahukura Peninsula

The Tapora Landcare Group, operating on the Okahukura Peninsula, has the long-term goal of making this region predator fenced. The aim of this study was to obtain information on the current status of avian biodiversity and the bird community across the band of coastal wetlands on the Okahukura Peninsula. Bird counts were conducted and playback lures used to detect three cryptic wetland species: fernbirds (Bowdleria punctata); spotless crakes (Porzana tabuensis); and banded rails (Gallirallus philippensis). Fernbirds and banded rails were detected at seven of the eight wetland sites sampled whereas spotless crakes were detected at two sites. The native species with the highest relative abundance across the eight sites were silvereyes (Zosterops lateralis) and South Island pied oystercatchers (Haematopus finschi). Changes in avian biodiversity over time in the region can now be monitored, and comprehensive long-term data on the status of avian biodiversity over time obtained.     

The nucleotide sequence of arginine tRNACCG from bovine liver

The nuclotide sequence of arginine tRNA(CCG) from bovine liver was determined to be: pG-A-C-C-C-A-G-U-m(1)G-m(2)G-C-C-U-A-A-D-Gm-G-A-D-A-A-G-G-C-A-psi-C-A-G-C-Cm-U-C-C-G-m(1)G-A-G-C-U-G-G-G-G-A-D-U-G-psi-G-G-G-T-psi-C-G-m(1)A-G-U-C-C-C-A-U-C-U-G-G-G-U-C-G-C-C-A(OH). This arginine tRNA is 76 nucleotides in length with 13 modified bases and has an anticodon of CCG. The sequence of this molecule is substantially different from those of other arginine tRNAs sequenced to date and is the only arginine tRNA sequenced which would be expected to recognize the codon CGG.Images     

The nucleotide sequence of spinach chloroplast methionine elongator tRNA.

The nucleotide sequence of spinach chloroplast methionine elongator tRNA (sp. chl. tRNAm Met) has been determined. This tRNA is considerably more homologous to E. coli tRNAm Met (67% homology) than to the three known eukaryotic tRNAm Met (50-55% homology). Sp. chl. tRNAm Met, like the eight other chloroplast tRNAs sequenced, contains a methylated GG sequence in the dihydrouridine loop and lacks unusual structural features which have been found in several mitochondrial tRNAs.     

Messenger ribonucleic acid of the lipoprotein of the Escherichia coli outer membrane. II. The complete nucleotide sequence

The complete nucleotide sequence of the mRNA for the outer membrane lipoprotein from Escherichia coli has been determined. All the ribonuclease T1 and ribonuclease A fragments obtained from the mRNA were connected with DNA sequencing of restriction endonuclease fragments of the cloned lipoprotein gene. The mRNA consists of 322 nucleotides, and there are 38 and 50 nucleotides in the 5' and 3' end untranslated regions, respectively. The mRNA has several unique features: (a) Out of 50 possible codons for 15 amino acids in the prolipoprotein only 25 codons are used, and all of these appear to be read by the major isoaccepting species of tRNAs for individual amino acids. (b) In the first 64 nucleotides from the 5' end, there are no obvious secondary structures. On the other hand, between the 65th nucleotide and the 3' end, 85% of the nucleotides are involved in the formation of secondary structures, with nine stable stem-and-loop structures. (c) There are many repeating sequences including one repeat of 40 nucleotides. (d) There are a few other features which could be important for efficient translation of the mRNA.     

Transit rights and U.S. security interests in international straits: The “straits debate”; revisited

Abstract

The issue of transit rights through international straits overlapped by an extension of territorial seas to 12nm was the focal point of intense debate between the United States and straits states during the formative stages of UNCLOS III. Even though the ICNT provisions on transit through straits reflect basic U.S. navigation and security interests, this paper argues that the issue of transit rights through straits is not a dead issue. Straits states may either refuse to ratify a LOS treaty incorporating ICNT provisions on transit passage, or the attempts to obtain a comprehensive LOS treaty may end in failure. In either case, the United States may be forced to accept a right of innocent passage through international straits. The conclusions of this paper are that the security of transit will be determined by political rather than legal considerations, and that U.S. security interests in straits are not undermined by a right of innocent passage.     

Molecular phylogeny of the springhare, Pedetes capensis, based on mitochondrial DNA sequences

The phylogenetic position of the Pedetidae, represented by a single species Pedetes capensis, is controversial, reflecting in part the retention of both Hystricomorphous and Sciurognathous characteristics in this rodent. In an attempt to clarify the species evolutionary relationships, mtDNA gene sequences from 10 rodent species (representing seven families) were analyzed using phenetic, parsimony, and maximum-likelihood methods of phylogenetic inference; the rabbit, Oryctolagus cuniculus (Order Lagomorpha), and cow, Bos taurus (Order Artiodactyla), were used as outgroups. Investigation of 714 base pairs of the protein-coding cytochrome b gene indicate strong base bias at the third codon position with significant rate heterogeneity evident between the three structural domains of this gene. Similar analyses conducted on 816 base pairs of the 12S rRNA gene revealed a transversion bias in the loop sections of all taxa. The cytochrome b gene sequences proved useful in resolving associations between closely related species but failed to produce consistent tree topologies at the family level. In contrast, phylogenetic analysis of the 12S rRNA gene resulted in strong support for the clustering of Pedetidae/Heteromyidae/Geomyidae and Muridae in one clade to the exclusion of the Hystricidae/Thryonomyidae and Sciuridae, a finding which is concordant with studies of rodent fetal membranes as well as reproductive and other anatomical features.