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.      

The MRN-CtIP Pathway Is Required for Metaphase Chromosome Alignment

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Highlights? The MRN-CtIP pathway is required for metaphase chromosome alignment in egg extracts ? MRN inhibition interferes with spindle assembly around DNA-coated beads ? MRN inhibition in cells causes a metaphase delay and disrupts the RanGTP gradient ? The MRN complex regulates the stable association of RCC1 to chromatin     

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     

RAD51 supports spontaneous non-homologous recombination in mammalian cells, but not the corresponding process induced by topoisomerase inhibitors

The RAD51 protein has been shown to participate in homologous recombination by promoting ATP-dependent homologous pairing and strand transfer reactions. In the present study, we have investigated the possible involvement of RAD51 in non-homologous recombination. We demonstrate that overexpression of CgRAD51 enhances the frequency of spontaneous non-homologous recombination in the hprt gene of Chinese hamster cells. However, the rate of non-homologous recombination induced by the topoisomerase inhibitors campothecin and etoposide was not altered by overexpression of RAD51. These results indicate that the RAD51 protein may perform a function in connection with spontaneous non-homologous recombination that is not essential to or not rate-limiting for non-homologous recombination induced by camptothecin or etoposide. We discuss the possibility that the role played by RAD51 in non-homologous recombination observed here may not be linked to non-homologous end-joining.     

The normal reaction of sinocarotidian origin in the rabbit]

Spontaneous changes of respiratory rate and blood pressure in the slightly anesthetized rabbit, contemporaneous with hippocampal synchronization, might be related with abrupt changes of the alertness. Registration of arousal reaction in hippocampal, thalamic and cortical leads, elicited by Hering nerve stimulation, shows that baro- and chemosensitive afferences may induce activation of areas which are usually involved in conditioning process.