Stigma development in Nicotiana tabacum. Cell death in transgenic plants as a marker to follow cell fate at high resolution

Pistil development was studied in transgenic tobacco plants in which the stigma is ablated by expression of a stigma-specific cytotoxic gene. These plants offer a tool to investigate the process of differentiation of the secretory zone, in that cell death caused by barnase activity provides a marker to follow cell fate at high resolution. After fusion of the carpel walls in the region most distal from the ovary, the epidermal cells begin to divide in both wild-type and stigmaless plants. Divisions of the L1 layer of the pistil are immediately followed by the morphogenetic events that lead to three different cell types: rounded-angular cells showing an equal number of anti- and periclinal divisions, cells that are more oblong forming the transition zone, and the square cells of the transmitting tissue dividing mostly anticlinally with respect to the original carpel wall. In the stigmaless plants, cell death caused by the expression ofSTIG 1-barnase begins at stage –1 and proceeds gradually, but is always associated with round epidermal cells and with angular-rounded cells underneath them. Studies at the ultrastructural level show that cell death caused by barnase activity occurs first in solitary cells and gradually extends to groups of cells.In situ hybridizations using the STIG 1 RNA probe in wild-type pistils confirm these results. Most likely, the cells in whichSTIG 1 is expressed are those that have just differentiated into the secretory cell type. Our results indicate that the transition zone or neck is autonomously differentiated from the secretory zone and the transmitting tissue. Furthermore, our results indicate that in both wild-type and stigmaless pistils secretion of lipids most likely occurs through the plasmodesmata. This observation suggests that bulk transport can occur via plasmodesmata.     

The effects of laser repetition rate on femtosecond laser ablation of dry bone: a thermal and LIBS study

The aim of this study is to understand the effect of varying laser repetition rate on thermal energy accumulation and dissipation as well as femtosecond Laser Induced Breakdown Spectroscopy (fsLIBS) signals, which may help create the framework for clinical translation of femtosecond lasers for surgical procedures. We study the effect of repetition rates on ablation widths, sample temperature, and LIBS signal of bone. SEM images were acquired to quantify the morphology of the ablated volume and fsLIBS was performed to characterize changes in signal intensity and background. We also report for the first time experimentally measured temperature distributions of bone irradiated with femtosecond lasers at repetition rates below and above carbonization conditions. While high repetition rates would allow for faster cutting, heat accumulation exceeds heat dissipation and results in carbonization of the sample. At repetition rates where carbonization occurs, the sample temperature increases to a level that is well above the threshold for irreversible cellular damage. These results highlight the importance of the need for careful selection of the repetition rate for a femtosecond laser surgery procedure to minimize the extent of thermal damage to surrounding tissues and prevent misclassification of tissue by fsLIBS analysis.

     

Genetic containment of forest plantations

Dispersal of pollen, seeds, or vegetative propagules from intensively bred, exotic, or recombinant DNA modified forest plantations may cause detrimental or beneficial ecological impacts on wild or managed ecosystems. Insertion of genes designed to prevent or substantially reduce dispersal could reduce the risk and extent of undesired impacts. Containment measures may also be required by law or marketplace constraints, regardless of risks or benefits. We discuss: (1) the context for when genetic containment or mitigation systems may be needed; (2) technology approaches and mechanisms; (3) the state of knowledge on genes/genomics of sexual reproduction in forest trees; (4) stability of transgene expression during vegetative growth; (5) simulation studies to define the level of containment needed; and (6) needed research to deliver effective containment technologies. We illustrate progress with several examples from our research on recombinant DNA modified poplars. Our simulations show that even partial sterility can provide very substantial reductions in gene flow into wild trees. We conclude that it is impossible to define the most effective containment approaches, nor their reliability, based on current genomic knowledge and technological tools. Additional genomic and technological studies of a wide variety of options are needed. Studies in field environments are essential to provide data relevant to ecological analysis and regulatory decisions and need to be carried out in phylogenetically diverse representatives of the economically most important taxa of forest trees.

Remote magnetic navigation vs. manual navigation for ablation of ventricular tachycardia: a meta-analysis

Background

The purpose of this study was to prospectively evaluate the efficacy and safety of remote magnetic navigation (RMN) in comparison with manual catheter navigation (MCN) in performing ventricular tachycardia ablation.

Methods

An electronic search was performed using PubMed (1948–2013) and EMBASE (1974–2013) studies comparing RMN with MCN which were published prior to 31 December 2013. Outcomes of interest were as follows: acute success, recurrence rate, complications, total procedure and fluoroscopic times. Standard mean difference (SMD) and its 95 % confidence interval (CI) were used for continuous outcomes; odds ratios (OR) were reported for dichotomous variables.

Results

Four non-randomised studies, including a total of 328 patients, were identified. RMN was deployed in 191 patients. Acute success and long-term freedom from arrhythmias were not significantly different between the RMN and control groups (OR 1.845, 95 % CI 0.731–4.659, p = 0.195 and OR 0.676, 95 % CI 0.383–1.194, p = 0.177, respectively). RMN was associated with less peri-procedural complications (OR 0.279, 95 % CI 0.092–0.843, p = 0.024). Shorter procedural and fluoroscopy times were achieved (95 % CI -0.487 to -0.035, p = 0.024 and 95 % CI -1.467 to -0.984, p<0.001, respectively).

Conclusion

The acute and long-term success rates for VT ablation are equal between RMN and MCN, whereas the RMN-guided procedure can be performed with a lower complication rate and less procedural and fluoroscopic times. More prospective randomised trials will be needed to better evaluate the superior role of RMN for catheter ablation of ventricular tachycardia.     

Sequelae after AF ablation: Efficacy and Safety go Hand in Hand

Although nowadays performed on a routine basis, catheter ablation of atrial fibrillation is associated with the potential for major complications. Improving the safety remains therefore an important challenge. This article summarizes the different types of complications associated with AF ablation grouping them into clinically overt major complications, subclinical injury and permanent injury. Furthermore, it describes the potential predictors for complications and highlights the dynamic interplay between efficacy and safety.     

Radiofrequency Ablation Of Typical Atrial Flutter Via Right Subclavian/jugular Vein Access In A Patient With Implanted Filter In The Inferior Vena Cava

Radiofrequency ablation of Cavotricuspid Isthmus-dependent Atrial Flutter (CTI AFL), a usual and safe therapeutic procedure in interventional electrophysiology with a high success rate, aiming to induce permanent block of conduction over CTI, is normally performed via the femoral access, which allows practical access to the CTI through the inferior vena cava (IVC). In rare cases of obstruction of IVC, ablation of CTI can be performed only through the superior vena cava (SVC) access. We present a case of typical atrial flutter that was ablated through the right subclavian/jugular veins because of iatrogenic obstruction of the IVC due to a previously implanted thrombus filter. Furthermore we discuss about how we resolved access-related problems of instability during catheter ablation on CTI.     

Isthmus Dependent Atrial Flutter Cycle Length Correlates with Right Atrial Cross-Sectional Area

Background

Right atrial flutter cycle length can prolong in the presence of antiarrhythmic drug therapy. We hypothesized that the cycle length of right atrial isthmus dependent flutter would correlate with right atrial cross-sectional area measurements.

Methods

60 patients who underwent ablation for electrophysiologically proven isthmus dependent right atrial flutter, who were not on Class I or Class III antiarrhythmic drugs and had recent 2-dimensional echocardiographic data comprised the study group. Right atrial length and width were measured in the apical four chamber view. Cross-sectional area was estimated by multiplying the length and width. 35 patients had an atrial flutter rate ≥ 250 bpm (Normal Flutter Group) and 25 patients had an atrial flutter rate < 250 bpm (Slow Flutter Group).

Results

Mean atrial flutter rate was 283 bpm in the normal flutter group and 227 bpm in the slow flutter group. Mean atrial flutter cycle length was 213 ms in the Normal Flutter Group and 265 ms in the Slow Flutter Group (p< 0.0001). Mean right atrial cross sectional area was 1845 mm² in the Normal Flutter group and 2378 mm² in the Slow Flutter Group, (p< 0.0001). Using linear regression, CSA was a significant predictor of cycle length (β =0.014 p = 0.0045). For every 1 mm² increase in cross-sectional area, cycle length is 0.014 ms longer.

Conclusions

In the absence of antiarrhythmic medications, right atrial cross sectional area enlargement correlates with atrial flutter cycle length. These findings provide further evidence that historical rate-related definitions of typical isthmus dependent right atrial are not mechanistically valid.     

An in vivo comparison of radiofrequency cardiac lesions formed by standard and magnetically steered 4 mm tip catheters

Background. In vivo comparison of cardiac radiofrequency ablation lesions between standard and magnetically steered 4 mm tip catheters has never been reported. Methods. High and low right atrium (RA) free wall, isthmus, right ventricle (RV) free wall and outflow tract lesions were studied macroscopically and microscopically five days after lesion formation in seven pigs. Shape, size, thrombus formation, and ablation parameters were compared. The effect of minimal, medium and high wall contact was assessed by a contact measurement utility for magnetic catheters. Results. All 14 RA free wall lesions were transmural with a similar epicardial and endocardial surface area. In the RV, the epicardial area usually appeared to be smaller than the endocardial area with standard catheters. Isthmus lesions were difficult to assess transmurality. There was no difference in endocardial area: standard 39 mm² (range 16 to 82 mm²) vs. magnetic 36 mm² (range 23 to 111 mm²). If the catheter tip was perpendicular to the tissue, magnetic lesions were more often round or oval, while standard lesions were more often elongated (p<0.05). When the catheter tip was parallel to tissue, lesions always tended to be elongated. Microscopic characteristics were similar. The contact utility was not useful. Average impedance (p<0.0001) and energy delivered (p<0.05) were less with magnetic catheters. Conclusion. Lesions from magnetically steered catheters are transmural of similar size, but with less variability than standard catheter lesions when the tip is perpendicular to the tissue. Magnetic lesions are associated with lower impedance and energy delivery. This suggests a more stable tip-to-tissue contact. (Neth Heart J 2010;18:66–71.)     

XeCl准分子激光消融几种生物组织的实验结果

本文报道了３０８ｎｍＸｅＣｌ准分子激光对人牙硬组织和猪肉软组织消融的实验研究结果,在国内首次开展了ＸｅＣｌ准分子激光牙科应用的基础研究,为准分子激光在牙科的临床应用提供了实验依据。