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.      

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     

Differences in lower-extremity muscular activation during walking between healthy older and young adults

Previous studies have identified differences in gait kinetics between healthy older and young adults. However, the underlying factors that cause these changes are not well understood. The objective of this study was to assess the effects of age and speed on the activation of lower-extremity muscles during human walking. We recorded electromyography (EMG) signals of the soleus, gastrocnemius, biceps femoris, medial hamstrings, tibialis anterior, vastus lateralis, and rectus femoris as healthy young and older adults walked over ground at slow, preferred and fast walking speeds. Nineteen healthy older adults (age, 73 ± 5 years) and 18 healthy young adults (age, 26 ± 3 years) participated. Rectified EMG signals were normalized to mean activities over a gait cycle at the preferred speed, allowing for an assessment of how the activity was distributed over the gait cycle and modulated with speed. Compared to the young adults, the older adults exhibited greater activation of the tibialis anterior and soleus during mid-stance at all walking speeds and greater activation of the vastus lateralis and medial hamstrings during loading and mid-stance at the fast walking speed, suggesting increased coactivation across the ankle and knee. In addition, older adults depend less on soleus muscle activation to push off at faster walking speeds. We conclude that age-related changes in neuromuscular activity reflect a strategy of stiffening the limb during single support and likely contribute to reduced push off power at fast walking speeds.     

Limitations in the use and interpretation of continuous relative phase

Continuous relative phase (CRP), a variable used to quantify intersegmental coordination, is difficult to interpret if care is not taken regarding the assumptions and limitations of the measure. Specifically, CRP is often interpreted as a higher resolution form of discrete relative phase (DRP). DRP, however, yields information regarding the relative dispersion of events in oscillatory signals while CRP describes their relationship in a higher order phase-plane domain. In this paper we address issues surrounding the calculation of CRP and suggest a new interpretation based on the aforementioned methodological issues. Through the use of test signals, with known properties, it was found that the CRP information will be arbitrary if no normalization procedures are used to account for frequency differences in the component oscillators. In addition, signals with non-sinusoidal trajectories will produce patterns in CRP that are not equivalent to discrete relative phase (DRP) measures. The implications of these issues are discussed.     

Amphibian Melanophore Technology as a Functional Screen for Antagonists of G-Protein Coupled 7-Transmembrane Receptors

Xenopus laevis melanophores stably expressing 7-transmembrane G-protein-coupled receptors were established and evaluated, either as a primary screening utility for antagonists of the human calcium receptor, or as a screen to assign function to binding inhibitors of human cannabinoid receptors. Stably or transiently expressing melanophores responded selectively to respective effectors of the human calcium, cannabinoid, and neurokinin-1 receptors. Several selective cannabinoid receptor-binding inhibitors of known potency were characterized as agonists or antagonists of the human peripheral cannabinoid (CB(2)) receptor. The results were consistent with changes in cAMP content of hCB(2)-transfected human embryonic kidney (HEK) cells challenged with the same CB(2)-binding antagonists. A stable melanophore cell line expressing the human calcium receptor was used to screen a compound collection directly for functional antagonists, several of which were confirmed as antagonists in secondary screens by stimulating parathyroid hormone (PTH) secretion from bovine parathyroid cells. The percentage of hits in this cell-based screen was reasonably low (1.2%), indicating minimal interference due to toxic effects and validating melanophores as a primary screening modality. Also described is the development of a novel procedure for cryopreservation and reconstitution of cells retaining functional human receptors. ()     

Active and passive contributions to joint kinetics during walking in older adults

The objectives of this study were to characterize the active and passive contributions to joint kinetics during walking in healthy young and older adults, and assess whether isokinetic ankle strength is associated with ankle power output during walking. Twenty healthy young (18–35 years) and 20 healthy older (65–85 years) adults participated in this study. We measured subject-specific passive-elastic joint moment–angle relationships in the lower extremity and tested maximum isokinetic ankle strength at 30 deg/s. Passive moment–angle relationships were used to estimate active and passive joint moment, power, and work quantities during walking at 80%, 100% and 120% of preferred walking speed. There were no significant differences in walking speed, step length, or cadence between the older and young adults. However, the older adults produced significantly more net positive work at the hip but less net positive work at the ankle at all walking speeds. Passive contributions to hip and ankle work did not significantly differ between groups, inferring that the older adults generated the additional hip work actively. Maximum isokinetic ankle strength was significantly less in the older adults, and correlated with peak positive plantar-flexor power at both the preferred and fast walking speeds. The results of this study suggest that age-related shifts in joint kinetics do not arise as a result of increased passive hip joint stiffness, but seem to be reflected in plantar-flexor weakness.