Effectiveness of Cover Crop Termination Methods on No-Till Cantaloupe

In a no-till system, there are many different methods available for terminating cover crops. Mechanical termination, utilizing rolling and crimping technology, is one method that injures the plant without cutting the stems. Another popular and commercially available method is mowing, but this can cause problems with cover crop re-growth and loose residue interfering with the planter during cash crop planting. A field experiment was conducted over three growing seasons in northern Alabama to determine the effects of different cover crops and termination methods on cantaloupe yield in a no-till system. Crimson clover, cereal rye, and hairy vetch cover crops were terminated using two different roller-crimpers, including a two-stage roller-crimper for four-wheel tractors and a powered roller-crimper for a two-wheel walk-behind tractor. Cover crop termination rates were evaluated one, two, and three weeks after termination. Three weeks after rolling, a higher termination rate was found for flail mowing (92%) compared to lower termination rates for a two-stage roller (86%) and powered roller-crimper (85%), while the control termination rate was only 49%. There were no significant differences in cantaloupe yield among the rolling treatments, which averaged 38,666 kg ha−1. However, yields were higher for cereal rye and hairy vetch cover crops (41,785 kg ha−1 and 42,000 kg ha−1) compared to crimson clover (32,213 kg ha−1).

CTELS: A Cell-Free System for the Analysis of Translation Termination Rate

Translation termination is the final step in protein biosynthesis when the synthesized polypeptide is released from the ribosome. Understanding this complex process is important for treatment of many human disorders caused by nonsense mutations in important genes. Here, we present a new method for the analysis of translation termination rate in cell-free systems, CTELS (for C-terminally extended luciferase-based system). This approach was based on a continuously measured luciferase activity during in vitro translation reaction of two reporter mRNA, one of which encodes a C-terminally extended luciferase. This extension occupies a ribosomal polypeptide tunnel and lets the completely synthesized enzyme be active before translation termination occurs, i.e., when it is still on the ribosome. In contrast, luciferase molecule without the extension emits light only after its release. Comparing the translation dynamics of these two reporters allows visualization of a delay corresponding to the translation termination event. We demonstrated applicability of this approach for investigating the effects of cis- and trans-acting components, including small molecule inhibitors and read-through inducing sequences, on the translation termination rate. With CTELS, we systematically assessed negative effects of decreased 3′ UTR length, specifically on termination. We also showed that blasticidin S implements its inhibitory effect on eukaryotic translation system, mostly by affecting elongation, and that an excess of eRF1 termination factor (both the wild-type and a non-catalytic AGQ mutant) can interfere with elongation. Analysis of read-through mechanics with CTELS revealed a transient stalling event at a “leaky” stop codon context, which likely defines the basis of nonsense suppression.

Aglepristone and cloprostenol combination in the termination of late-term pregnancy in queens

Objectives Termination rates for the highly recommended aglepristone (AGL) treatment are low in late-term pregnancy in queens. We studied the effects of an AGL and cloprostenol (CLO) combination in the termination of late-term pregnancy. Methods Pregnant queens were assigned to two groups. Queens in the AGL group (n = 10) received AGL 10 mg/kg, twice, 24 h apart. Queens in the AGL-CLO group (n = 9) were additionally injected with a single dose of CLO (5 μg/kg) 24 h after the second dose of AGL. Progesterone, 17beta(β)-oestradiol, cortisol, oxytocin and prostaglandin F2alpha (PGF2α) metabolite were measured in sera obtained at days 0, 1 and 2, and on the day of abortion. Results Average gestational age in both groups was similar (AGL 38.61 ± 0.91 days vs AGL-CLO 39.39 ± 1.35 days; P >0.05). Termination rates were 80% and 100% in the AGL and AGL-CLO groups, respectively ( P <0.05). Fetal expulsion time was significantly longer ( P <0.001) in the AGL group (96.9 ± 6 h) compared with the AGL-CLO group (69.8 ± 3.3 h). Duration of abortion was 19.8 ± 2.6 h and 12.6 ± 1.4 h in the AGL and AGL-CLO groups, respectively ( P <0.05). Both treatments were well tolerated. Significantly ( P <0.05) lower serum progesterone concentrations were observed in both groups at the day of abortion and concentrations in the AGL-CLO group (4.19 ± 0.80 ng/ml) were lower than in the AGL group (9.89 ± 2.21 ng/ml; P <0.05). Conclusions and relevance AGL and CLO combination increases pregnancy termination rate in late-term pregnant queens. In addition, CLO contributes to a decrease in luteal function in AGL-treated late-term pregnant queens.

P6593Comparison of the termination effects between multi-segment continuous illumination and anti-tachycardia pacing on myocardial infarction ventricular arrhythmia

Introduction Anti-tachycardia pacing (ATP) therapy is an important treatment for current ICD termination of ventricular arrhythmia (VA). But there was concern about excessive frequency and voltage can cause arrhythmia, pain and damage. Optogenetic allowed modulation of electrical excitation with light in myocardium over-expressing light-sensitive protein, and optical illumination developed a non-contact and pain-free approach to research and treatment of cardiac disorder. Purpose Explore the effects of optogenetic termination and electric termination of myocardial infarction VA in vivo. Methods Rats (N=10) accepted jugular vein injection with 1×1012 vector genomes of (AAV-CAG-hChR2(H134R)-mcherry) to achieve cardiac transgenic expression of light sensitive protein Channelrhodopsin-2 (ChR2). After thoracotomy, myocardial infarction was induced by ligation of the left anterior descending coronary artery, and then VA was induced by electrical burst stimulation (10 v, 50 Hz, 2 s). Before the myocardial infarction operation, every heart was illuminated by 473 nm laser or electrical stimulated on the right ventricle in a train of 30 pulses at 8 HZ to test the threshold of light intensity or electrical pacing voltage. The VA termination process during 20 s after burst stimulation was investigated in different performance: optical termination, 1 s constant illumination repeated in 4 episodes with 1 s interval (470 nm, 20 times threshold intensity); electrical termination, ATP in 8 pulses of 8hz with 2ms duration in 4 times pacing threshold; natural recovery from VA, without optical or electrical intervention. Recovery time was defined as the time from the end of the burst stimulation to the recovery of sinus rhythm, and the termination rate was the percentage of sinus rhythm recovery among 11s after the end of burst stimulation with or without any intervention. Results We analyzed the recovery time and the termination rate (N=10, n=127 episodes per mode). The sequence of recovery time was optical termination (7.328±0.3623 s) < electric termination (10.31±0.4482 s) < natural recovery (12.97±0.3834 s) (figure D). We confirmed that the termination rate of optical illumination (86.14±4.145%) was higher than those of ATP (63.5±6.371%) and natural recovery (47.71±5.476%) (figure E), and there was no significant difference between the last two process (one-way of ANOVA; p=0.124). Comparison of three modes Conclusions Optogenetic manipulation shortened the recovery time and increased the termination rate in myocardial infarction ventricular arrhythmia, which may provide a potential approach for translational arrhythmia therapy. Acknowledgement/Funding The national natural science foundation of China (81772044)

Trigger loop dynamics can explain stimulation of intrinsic termination by bacterial RNA polymerase without terminator hairpin contact

In bacteria, intrinsic termination signals cause disassembly of the highly stable elongating transcription complex (EC) over windows of two to three nucleotides after kilobases of RNA synthesis. Intrinsic termination is caused by the formation of a nascent RNA hairpin adjacent to a weak RNA−DNA hybrid within RNA polymerase (RNAP). Although the contributions of RNA and DNA sequences to termination are largely understood, the roles of conformational changes in RNAP are less well described. The polymorphous trigger loop (TL), which folds into the trigger helices to promote nucleotide addition, also is proposed to drive termination by folding into the trigger helices and contacting the terminator hairpin after invasion of the hairpin in the RNAP main cleft [Epshtein V, Cardinale CJ, Ruckenstein AE, Borukhov S, Nudler E (2007) Mol Cell 28:991–1001]. To investigate the contribution of the TL to intrinsic termination, we developed a kinetic assay that distinguishes effects of TL alterations on the rate at which ECs terminate from effects of the TL on the nucleotide addition rate that indirectly affect termination efficiency by altering the time window in which termination can occur. We confirmed that the TL stimulates termination rate, but found that stabilizing either the folded or unfolded TL conformation decreased termination rate. We propose that conformational fluctuations of the TL (TL dynamics), not TL-hairpin contact, aid termination by increasing EC conformational diversity and thus access to favorable termination pathways. We also report that the TL and the TL sequence insertion (SI3) increase overall termination efficiency by stimulating pausing, which increases the flux of ECs into the termination pathway.