Increasing atmospheric CO2 concentrations ([CO2]) in agricultural and natural ecosystems is known to reduce plant stomatal opening, but it is unclear whether these CO2-induced stomatal alterations are associated with foliar pathogen infections. In this study, tomato plants were grown under ambient and elevated [CO2] and inoculated with Pseudomonas syringae pv. tomato strain DC3000, a strain that is virulent on tomato plants. We found that elevated [CO2] enhanced tomato defence against P. syringae. Scanning electron microscopy analysis revealed that stomatal aperture of elevated [CO2] plants was considerably smaller than their ambient counterparts, which affected the behaviour of P. syringae bacteria on the upper surface of epidermal peels. Pharmacological experiments revealed that nitric oxide (NO) played a role in elevated [CO2]-induced stomatal closure. Silencing key genes involved in NO generation and stomatal closing, nitrate reductase (NR) and guard cell slow-type anion channel 1 (SLAC1), blocked elevated [CO2]-induced stomatal closure and resulted in significant increases in P. syringae infection. However, the SLAC1-silenced plants, but not the NR-silenced plants, still had significantly higher defence under elevated [CO2] compared with plants treated with ambient [CO2]. Similar results were obtained when the stomata-limiting factor for P. syringae entry was excluded by syringe infiltration inoculation. These results indicate that elevated [CO2] induces defence against P. syringae in tomato plants, not only by reducing the stomata-mediated entry of P. syringae but also by invoking a stomata-independent pathway to counteract P. syringae. This information is valuable for designing proper strategies against bacterial pathogens under changing agricultural and natural ecosystems.
A porcine reproductive and respiratory syndrome virus (PRRSV) QY1 was serially passed on Marc-145 cells. Virulence of different intermediate derivatives of QY1 (P5, P60, P80, and P100) were determined. The study found that QY1 had been gradually attenuated during the in vitro process. Pathogenicity study showed that pigs inoculated with QY1 P100 and P80 did not develop any significant PRRS clinic symptoms. However, mild-to-moderate clinical signs and acute HP-PRRSV symptoms of infection were observed in pigs inoculated with QY1 P60 and P5, respectively. Furthermore, we determined the whole genome sequences of these four intermediate viruses. The results showed that after 100 passages, compared to QY1 P5, a total of 32 amino acid mutations were found. Moreover, there were one nucleotide deletion and a unique 34-amino acid deletion found at 5'UTR and in nsp2 gene during the attenuation process, respectively. Such deletions were genetically stable in vivo. Following PRRSV experimental challenge, pigs inoculated with a single dose of QY1 P100 developed no significant clinic symptoms and well tolerated lethal challenge, while QY1 P80 group still developed mild fever in the clinic trial after challenge. Thus, we concluded that QY1 P100 was a promising and highly attenuated PRRSV vaccine candidate.
Pulse wave velocity (PWV) is the most important index of arterial stiffness. It is conventionally estimated by noninvasively measuring central and peripheral blood pressure (BP) and/or velocity (BV) waveforms and then detecting the foot-tofoot time delay between the waveforms wherein wave reflection is presumed absent. We developed techniques for improved estimation of PWV from the same waveforms. The techniques effectively estimate PWV from the entire waveforms, rather than just their feet, by mathematically eliminating the reflected wave via an arterial tube-load model. In this way, the techniques may be more robust to artifact while revealing the true PWV in absence of wave reflection. We applied the techniques to estimate aortic PWV from simultaneously and sequentially measured central and peripheral BP waveforms and simultaneously measured central BV and peripheral BP waveforms from 17 anesthetized animals during diverse interventions that perturbed BP widely. Since BP is the major acute determinant of aortic PWV, especially under anesthesia wherein vasomotor tone changes are minimal, we evaluated the techniques in terms of the ability of their PWV estimates to track the acute BP changes in each subject. Overall, the PWV estimates of the techniques tracked the BP changes better than those of the conventional technique (e.g., diastolic BP root-meansquared- errors of 3.4 vs. 5.2 mmHg for the simultaneous BP waveforms and 7.0 vs. 12.2 mmHg for the BV and BP waveforms (p < 0.02)). With further testing, the arterial tube-load modelbased PWV estimation techniques may afford more accurate arterial stiffness monitoring in hypertensive and other patients.
It is widely accepted that leaf dark respiration is a determining factor for the growth and maintenance of plant tissues and the carbon cycle. However, the underlying effect and mechanism of elevated CO2 concentrations ([CO2]) on dark respiration remain unclear. In this study, tomato plants grown at elevated [CO2] showed consistently higher leaf dark respiratory rate, as compared with ambient control plants. The increased respiratory capacity was driven by a greater abundance of proteins, carbohydrates, and transcripts involved in pathways of glycolysis carbohydrate metabolism, the tricarboxylic acid cycle, and mitochondrial electron transport energy metabolism. This study provides substantial evidence in support of the concept that leaf dark respiration is increased by elevated [CO2] in tomato plants and suggests that the increased availability of carbohydrates and the increased energy status are involved in the increased rate of dark respiration in response to elevated [CO2].
Pulse transit time (PTT) is a proven, simple to measure, marker of blood pressure (BP) that could potentially permit continuous, noninvasive, and cuff-less BP monitoring (after an initial calibration). However, pulse arrival time (PAT), which is equal to the sum of PTT and the pre-ejection period, is gaining popularity for BP tracking, because it is even simpler to measure. The aim of this study was to evaluate the hypothesis that PAT is an adequate surrogate for PTT as a marker of BP. PAT and PTT were estimated through the aorta using high-fidelity invasive arterial waveforms obtained from six dogs during wide BP changes induced by multiple interventions. These time delays and their reciprocals were evaluated in terms of their ability to predict diastolic, mean, and systolic BP (DBP, MBP, and SBP) per animal. The root mean squared error (RMSE) between the BP parameter predicted via the time delay and the measured BP parameter was specifically used as the evaluation metric. Taking the reciprocals of the time delays tended to reduce the RMSE values. The DBP, MBP, and SBP RMSE values for 1/PAT were 9.8 ± 5.2, 10.4 ± 5.6, and 11.9 ± 6.1 mmHg, whereas the corresponding values for 1/PTT were 5.3 ± 1.2, 4.8 ± 1.0, and 7.5 ± 2.2 mmHg (P < 0.05). Thus tracking BP via PAT was not only markedly worse than via PTT but also unable to meet the FDA BP error limits. In contrast to previous studies, our results quantitatively indicate that PAT is not an adequate surrogate for PTT in terms of detecting challenging BP changes.
We compared pulse arrival time (PAT) and pulse transit time (PTT) in terms of their ability to track diastolic pressure (DP). We performed the comparison using high fidelity, invasive arterial waveforms recorded from six dogs during multiple interventions. On average, DP ranged from 40 to 106 mmHg and therefore varied widely. PAT and PTT were able to predict DP with average root-mean-squared-errors of 9.8 ± 5.8 mmHg and 5.7 ± 2.0 mmHg (p = 0.02). Thus, even though PAT is simpler to measure, we can only recommend using PTT for tracking DP.
We previously developed a technique for estimating relative cardiac output (CO) change by long time interval analysis of a radial arterial blood pressure waveform. This technique analyzes the slow, beat-to-beat changes in the waveform to circumvent the confounding wave reflections but assumes constant arterial compliance (AC). Here, we sought to correct the CO estimates of the technique for potential AC changes using pulse transit time--a conveniently measured index of AC. For proof-of-concept, we compared the original and corrected techniques using invasive swine hemodynamic data. The corrected technique reduced the overall calibrated CO estimation error by 18% relative to the original technique.
We proposed a technique for estimating beat-to-beat pulse transit time (PTT) from central and peripheral blood pressure or flow waveforms based on an arterial tube-load model of wave reflection. The technique effectively estimates PTT from the entire waveforms after mathematically eliminating the reflected wave. So, unlike the conventional foot-to-foot detection technique, this technique should be robust to artifact while revealing the true PTT (i.e., the PTT in absence of wave reflection). We compared the two techniques, as applied to blood pressure and flow waveforms, in terms of the ability of their PTT estimates to correlate with blood pressure (a) during baseline (for which the naturally occurring beat-to-beat changes were small), (b) during low heart rate (wherein wave reflection was profound), and (c) in the presence of actual measurement artifact. In all three cases, the PTT estimates of the arterial tube-load model technique yielded markedly superior correlation to blood pressure.
A useful model of the arterial system is the uniform, lossless tube with parametric load. This tube-load model is able to account for wave propagation and reflection (unlike lumped-parameter models such as the Windkessel) while being defined by only a few parameters (unlike comprehensive distributed-parameter models). As a result, the parameters may be readily estimated by accurate fitting of the model to available arterial pressure and flow waveforms so as to permit improved monitoring of arterial hemodynamics. In this paper, we review tube-load model parameter estimation techniques that have appeared in the literature for monitoring wave reflection, large artery compliance, pulse transit time, and central aortic pressure. We begin by motivating the use of the tube-load model for parameter estimation. We then describe the tube-load model, its assumptions and validity, and approaches for estimating its parameters. We next summarize the various techniques and their experimental results while highlighting their advantages over conventional techniques. We conclude the review by suggesting future research directions and describing potential applications.
We investigated the system identification approach for potentially improved estimation of pulse transit time (PTT), a popular arterial stiffness marker. In this approach, proximal and distal arterial waveforms are measured and respectively regarded as the input and output of a system. Next, the system impulse response is identified from all samples of the measured input and output. Finally, the time delay of the impulse response is detected as the PTT estimate. Unlike conventional foot-to-foot detection techniques, this approach is designed to provide an artifact robust estimate of the true PTT in the absence of wave reflection. The approach is also applicable to arbitrary types of arterial waveforms. We specifically applied a parametric system identification technique to noninvasive impedance cardiography (ICG) and peripheral arterial blood pressure waveforms from 15 humans subjected to lower-body negative pressure. We assessed the technique through the correlation coefficient (r) between its 1/PTT estimates and measured diastolic pressure (DP) per subject and the root mean squared error (RMSE) of the DP predicted from these estimates and measured DP. The technique achieved average r and RMSE values of 0.81 ± 0.16 and 4.3 ± 1.3 mmHg. For comparison, the corresponding values were 0.59 ± 0.37 (P < 0.05) and 5.9 ± 2.5 (P < 0.01) mmHg for the conventional technique applied to the same waveforms and 0.28 ± 0.40 (P < 0.001) and 7.2 ± 1.8 (P < 0.001) mmHg for the conventional technique with the ECG waveform substituted for the ICG waveform. These results demonstrate, perhaps for the first time, that the system identification approach can indeed improve PTT estimation.
Pulse wave velocity (PWV) determined through the foot-to-foot time delay between carotid and femoral artery waveforms is an index of aortic stiffness with proven clinical value. However, handheld transducers, which are often used to non-invasively measure the waveforms, are prone to motion artifact that may limit the full potential of this index. Here, we conceived an artifact robust technique to estimate PWV based on an arterial tube model. We applied the technique to high fidelity canine arterial pressure waveforms before and after contamination with known amounts of noise. Our results showed that, as the signal-to-noise ratio decreased, the PWV estimates of the technique predicted diastolic and mean arterial pressure with increasingly greater accuracy than the PWV estimates of the conventional foot-to-foot detection technique.
Pulse wave velocity (PWV) is a marker of arterial stiffness and may permit continuous, non-invasive, and cuff-less monitoring of blood pressure. Here, robust PWV estimation was sought by application of system identification to proximal and distal arterial waveforms. In this approach, the system that optimally couples the proximal waveform to the distal waveform is identified, and the time delay of this system is then used to calculate PWV. To demonstrate proof-of-concept, a standard identification technique was applied to non-invasive impedance cardiography and peripheral arterial blood pressure waveforms from six humans subjected to progressive reductions in central blood volume induced by lower body negative pressure. This technique estimated diastolic pressure with an overall root-mean-squared-error of 5.2 mmHg. For comparison, the conventional detection method for estimating PWV yielded a corresponding error of 8.3 mmHg.
We recently proposed a technique to estimate relative cardiac output (CO) change by unique long time interval analysis (LTIA) of a radial arterial blood pressure waveform. Here, we evaluated the technique in 169 critically ill patients, while comparing it to previous "pulse contour analysis" techniques, using the public MIMIC II database. The LTIA technique achieved an overall calibrated CO error of 18.8% against reference (single determination) thermodilution measurements. This level of accuracy was not better than the previous techniques. However, the average absolute thermodilution CO change in each patient was only 12.3%. As the absolute CO change increased, the LTIA technique became increasingly more accurate than the previous techniques.
The genome of one isolate of porcine reproductive and respiratory syndrome virus (PRRSV) from China, designated GDQY2, was sequenced and analyzed. The full length of GDQY2 was 15,215 nucleotides, excluding the poly(A) tail. Comparative analysis with the genomic sequences of numerous worldwide North American isolates revealed that GDQY2 shared 85.0-98.9% identity with these isolates, but only 60.9% with the European virus-LV (Lelystad Virus), indicating that this new Chinese isolate was closely related to the North American PRRSV genotype. Phylogenetic analysis based on the nucleotide sequences of the full length and ORF5 showed that this new isolate belong to the same genetic group with all other Chinese isolates. Comparison with North American PRRSV isolates revealed that GDQY2 exhibited variations in the non-structural protein 2 (NSP2) encoded by ORF1a, namely that an additional 35-amino acid deletion in NSP2 was found in GDQY2. Therefore, GDQY2 was a novel strain with unique deletions. Furthermore, our study demonstrated that North American genotype PRRSVs in China have evolved independently from other countries, indicating that geographic separation might be one factor influencing the molecular evolution of PRRSV.
There is a profound need for early and convenient detection of hemorrhage in both civilian and military medicine. Due to wave reflection timing, central pulse pressure (PP), but not peripheral PP, is a surrogate of stroke volume (SV) and therefore an early marker of blood loss. However, only peripheral PP is convenient to measure. We tested an adaptive transfer function technique for deriving the central arterial blood pressure (ABP) waveform from a non-invasive peripheral ABP waveform in healthy humans subjected to lower body negative pressure (LBNP), a safe model of early hemorrhage. Our results showed that the derived central PP provided an earlier and more sensitive marker of progressive LBNP and a far more accurate measure of SV than measured peripheral PP.
Porcine reproductive and respiratory syndrome virus (PRRSV) continues to affect the Chinese swine industry. Since 2006, variant PRRSV strains sharing two unique discontinuous deletions of 30 amino acids in the nonstructural protein Nsp2 have become dominant in Chinese swine herds and have caused huge economic losses to the swine industry in China. Here we report the complete genome sequence of two novel PRRSV variants isolated from vaccinated piglets with additional amino acid deletions in Nsp2.
Porcine reproductive and respiratory syndrome virus (PRRSV) is the etiologic agent of porcine reproductive and respiratory syndrome (PRRS), which can evolve continuously by random mutation or intragenic recombination. Here we report the complete genomic sequence of a PRRSV variant with nucleotide acid deletions and insertions in the nonstructural protein 2 (nsp2) gene and a possible recombination event between a modified live virus (MLV) vaccine strain and a prototype Chinese field strain.
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