The effects of mispair and nonpair correction in hybrid DNA on base ratios (G + C content) and total amounts of DNA

Base ratios and total DNA amounts can vary substantially between and within higher taxa and genera, and even within species. Gene conversion is one of several mechanisms that could cause such changes. For base substitutions, disparity in conversion direction is accompanied by an equivalent disparity in base ratio at the heterozygous site. Disparity in the direction of gene conversion at meiosis is common and can be extreme. For transitions (which give purine [R]/pyrimidine [Y] mispairs) and for transversions giving unlike R/R and Y/Y mispairs in hybrid DNA, this disparity could give slow but systematic changes in G + C percentage. For transversions giving like R/R and Y/Y mispairs, it could change AT/TA and CG/GC ratios. From the extent of correction direction disparity, one can deduce properties of repair enzymes, such as the ability (1) to excise preferentially the purine from one mispair and the pyrimidine from the other for two different R/Y mispairs from a single heterozygous site and (2) to excise one base preferentially from unlike R/R or Y/Y mispairs. Frame-shifts usually show strong disparity in conversion direction, with preferential cutting of the nonlooped or the looped-out strand of the nonpair in heterozygous h-DNA. The opposite directions of disparity for frame-shifts and their intragenic suppressors as Ascobolus suggest that repair enzymes have a strong, systematic bias as to which strand is cut. The conversion spectra of mutations induced with different mutagens suggest that the nonlooped strand is preferentially cut, so that base additions generally convert to mutant and deletions generally convert to wild-type forms. Especially in nonfunctional or noncoding DNA, this could cause a general increase in DNA amounts. Conversion disparity, selection, mutation, and other processes interact, affecting rates of change in base ratios and total DNA.      

Low cell surface hydrophobicity is one of the key factors for high butanol tolerance of Lactic acid bacteria

Highly butanol‐tolerant strains have always been attractive because of their potential as microbial hosts for butanol production. However, due to the amphiphilic nature of 1‐butanol as a solvent, the relationship between the cell surface hydrophobicity and butanol resistance remained ambiguous to date. In this work, the quantitatively estimated cell surface hydrophobicity of 74 Lactic acid bacteria strains were juxtaposed to their tolerance to various butanol concentrations. The obtained results revealed that the strains’ hydrophobicity was inversely proportional to their butanol tolerance. All highly butanol‐resistant strains were hydrophilic (cell surface hydrophobicity<1%), whereas the more hydrophobic the strains were, the more sensitive to butanol they were. Furthermore, cultivation at increasing butanol concentrations showed a clear tendency to decrease the level of hydrophobicity in all tested organisms, thus suggesting possible adaptation mechanisms. Purposeful reduction of cell surface hydrophobicity (by removal of S‐layer proteins from the cell envelope) also led to an increase of butanol resistance. Since the results covered 23 different Lactic acid bacteria species of seven genera, it could be concluded that regardless of the species, the lower degree of cells’ hydrophobicity clearly correlates with the higher level of butanol tolerance.     

G Protein-coupled Receptor (GPCR) Signaling via Heterotrimeric G Proteins from Endosomes

Some G protein-coupled receptors (GPCRs), in addition to activating heterotrimeric G proteins in the plasma membrane, appear to elicit a “second wave” of G protein activation after ligand-induced internalization. We briefly summarize evidence supporting this view and then discuss what is presently known about the functional significance of GPCR-G protein activation in endosomes. Endosomal activation can shape the cellular response temporally by prolonging its overall duration, and may shape the response spatially by moving the location of intracellular second messenger production relative to effectors.     

Homogeneity of the 16S rDNA sequence among geographically disparate isolates of Taylorella equigenitalis

Background

At present, six accessible sequences of 16S rDNA from Taylorella equigenitalis (T. equigenitalis) are available, whose sequence differences occur at a few nucleotide positions. Thus it is important to determine these sequences from additional strains in other countries, if possible, in order to clarify any anomalies regarding 16S rDNA sequence heterogeneity. Here, we clone and sequence the approximate full-length 16S rDNA from additional strains of T. equigenitalis isolated in Japan, Australia and France and compare these sequences to the existing published sequences.

Results

Clarification of any anomalies regarding 16S rDNA sequence heterogeneity of T. equigenitalis was carried out. When cloning, sequencing and comparison of the approximate full-length 16S rDNA from 17 strains of T. equigenitalis isolated in Japan, Australia and France, nucleotide sequence differences were demonstrated at the six loci in the 1,469 nucleotide sequence. Moreover, 12 polymorphic sites occurred among 23 sequences of the 16S rDNA, including the six reference sequences.

Conclusion

High sequence similarity (99.5% or more) was observed throughout, except from nucleotide positions 138 to 501 where substitutions and deletions were noted.     

Temporal Variation in Seed Predation by Insects in a Population of Syagrus romanzoffiana (Arecaceae) in Santa Catarina Island, SC, Brazil

Insect seed predation may vary depending on seed production. The present study considers the hypothesis that the rates of seed predation tend to be smaller in years of higher fruit production. Thus, we monitored the production of fruits and predation of seeds of the palm Syagrus romanzoffiana over 2?years in the Atlantic Forest (Parque Municipal da Lagoa do Peri, Florianópolis, SC, Brazil), between July 2006 and June 2008. Plots of 0.25?m² were fitted under 20 mother plants and fruits were monthly collected for assessment of abundance and seed predation. There was variation in fruit production between the 2?years and among reproductive plants. Predation rates were high and occurred in the predispersal phase by the Curculionidae Revena rubiginosa Boheman, Anchylorhynchus aegrotus Fahraeus, and Anchylorhynchus variabilis Gyllenhal. Seed predation by these species of Anchylorhynchus is first registered in the present study. In average, about 60% of the seeds monthly produced in the population tend to escape insect predation in year of high or low production, becoming available for recruitment. The predation rate was not related to the amount of fruits produced per reproductive plant. Also, different than expected, there was a positive relation between the rates of seed predation and the total of fruits produced monthly on the plots. Thus, no evidence for the satiation of insect seed predators was found in this study with S. romanzoffiana.     

Desflurane consumption during automated closed-circuit delivery is higher than when a conventional anesthesia machine is used with a simple vaporizer-O2-N2O fresh gas flow sequence

Background

Current analgesics have drawbacks such as delays in acquisition, lag-times for effect, and side effects. We recently presented a preliminary report of a new analgesic method involving a two-minute sciatic nerve press, which resulted in immediate short-term relief of pain associated with dental and renal diseases. The present study investigated whether this technique was effective for pain associated with other disease types, and whether the relief was effective for up to one hour.

Methods

This randomized, placebo-controlled, parallel-group trial was conducted in four hospitals in Anhui Province, China. Patients with pain were sequentially recruited by participating physicians during clinic visits, and 135 patients aged 15 – 80 years were enrolled. Dental disease patients included those with acute pulpitis and periapical abscesses. Renal disease patients included those with kidney infections and/or stones. Tumor patients included those with nose, breast, stomach and liver cancers, while Emergency Room patients had various pathologies. Patients were randomly assigned to receive a "sciatic nerve press" in which pressure was applied simultaneously to the sciatic nerves at the back of both thighs, or a "placebo press" in which pressure was applied to a parallel region on the front of the thighs. Each fist applied a pressure of 11 – 20 kg for 2 minutes. Patients rated their level of pain before and after the procedure.

Results

The "sciatic nerve press" produced immediate relief of pain in all patient groups. Emergency patients reported a 43.5% reduction in pain (p < 0.001). Significant pain relief for dental, renal and tumor patients lasted for 60 minutes (p < 0.001). The peak pain relief occurred at the 10 – 20^th minutes, and the relief decreased 47% by the 60^th minutes.

Conclusion

Two minutes of pressure on both sciatic nerves produced immediate significant short-term conduction analgesia. This technique is a convenient, safe and powerful method for the short-term treatment of clinical pain associated with a diverse range of pathologies.

Trial registration

Current Controlled Trials ACTRN012606000439549     

Biosynthesis of tunicamycin and metabolic origin of the 11-carbon dialdose sugar,tunicamine

Tunicamycin is a reversible inhibitor of polyprenol-phosphate: N-acetylhexosamine-1-phosphate translocases and is produced by several Streptomyces species. We have examined tunicamycin biosynthesis, an important but poorly characterized biosynthetic pathway. Biosynthetic precursors have been identified by incorporating radioactive and stable isotopes, and by determining the labeling pattern using electrospray ionization-collision induced dissociation-mass spectrometry (ESI-CID-MS), and proton, deuterium, and C-13 nuclear magnetic resonance (NMR) spectroscopy. Preparation and analysis of [uracil-5-(2)H]-labeled tunicamycin established the complete ESI-CID-MS fragmentation pathway for the major components of the tunicamycin complex. Competitive metabolic experiments indicate that 7 deuteriums incorporate into tunicamycin from [6,6'-(2)H,(2)H]-labeled D-glucose, 6 of which arise from D-GlcNAc and 1 from uridine and/or D-ribose. Inverse correlation NMR experiments (heteronuclear single-quantum coherence (HSQC)) of (13)C-labeled tunicamycin enriched from D-[1-(13)C]glucose suggest that the unique tunicamine 11-carbon dialdose sugar backbone arises from a 5-carbon furanose precursor derived from uridine and a 6-carbon N-acetylamino-pyranose precursor derived from UDP-D-N-acetylglucosamine. The equivalent incorporation of (13)C into both the alpha-1" and beta-11' anomeric carbons of tunicamycin supports a direct biosynthesis via 6-carbon metabolism. It also indicates that the tunicamine motif and the alpha-1"-linked GlcNAc residue are both derived from the same metabolic pool of UDP-GlcNAc, without significant differential metabolic processing. A biosynthetic pathway is therefore proposed for tunicamycin for the first time: an initial formation of the 11-carbon tunicamine sugar motif from uridine and UDP-GlcNAc via uridine-5'-aldehyde and UDP-4-keto-6-ene-N-acetylhexosamine, respectively, and subsequent formation of the anomeric-to-anomeric alpha, beta-1",11'-glycosidic bond.